Problems with Paypal IPN/Sandbox environment

Hi, n00b here!

I'm trying to enable Paypal IPN here at work for our store. Right now, I'm testing on our development server. It's only accessible on our network, so I thought that might be giving me problems. I did set up the module to point to the 'ipn_main_handler.php' on our live server, but that didn't fix anything.

This is the response I get:

Sep 26 2007 9:13 -- IPN INFO - Confirmation/Validation response
5 
FAIL
0

The payment goes through (not sure if it should or shouldn't), but the order isn't stored in Zen Cart. I've read through plenty of posts here, but couldn't find a solution that works for me.

Any help/suggestions are appreciated.

P.S. Using sandbox because we don't have a Paypal account set up here at work just yet.

Install the ipncheck.php tool from here:
http://www.zen-cart.com/forum/showthread.php?t=65680

And post the results you get when running it with your browser.

FAQ: http://www.zen-cart.com/wiki/index.php/PayPal

Results from ipncheck.php

IPNCHECK.PHP - Version 1.0

IPN TESTING - POSTING to PayPal via: ssl://www.paypal.com:443

IPN TESTING - Confirmation/Validation response: RESPONSE RECEIVED - Communications OKAY


Script finished.

So is this just a lost cause now?

I do have the newest PayPal patch installed. The ipncheck seems to be working. I'm not sure what else I should be looking at. Just wait to test live?

1. The fact that ipncheck.php "worked" means that your server is allowing communications to happen from your server to PayPal.

It doesn't mean that it works the other way around. You only posted partial log details, so I can't really diagnose any further information about what is or isn't happening.

2. If your server cannot be reached by PayPal's servers (ie; accessed from the "outside world"), then you'll not be able to test the IPN incoming notifications, since it all happens based on actual communications between servers.

I was thinking that #2 was the main culprit. I tried setting up the IPN handler on our live server, but that didn't help anything.

I was just trying out Express Checkout today, and that appears to work. I'm not sure which module we will be using once we go live, so I just wanted to make sure both would work. Looks like I'm 1-1.

Anyway, thanks for your help.

Using curltest with ?paypal parameter I am receiving the following error message:

Array
(
    [url] => "https://api-3t.paypal.com/nvp"
    [content_type] => text/plain; charset=utf-8
    [http_code] => 200
    [header_size] => 215
    [request_size] => 166
    [filetime] => -1
    [ssl_verify_result] => 0
    [redirect_count] => 0
    [total_time] => 0.172195
    [namelookup_time] => 2.6E-5
    [connect_time] => 0.012365
    [pretransfer_time] => 0.050122
    [size_upload] => 37
    [size_download] => 146
    [speed_download] => 847
    [speed_upload] => 214
    [download_content_length] => 146
    [upload_content_length] => 0
    [starttransfer_time] => 0.172166
    [redirect_time] => 0
)



ACK=Failure&L_ERRORCODE0=81002&L_SHORTMESSAGE0=Unspecified%20Method&L_LONGMESSAGE0=Method%20Specified%20is%20not%20Supported&L_SEVERITYCODE0=ErrorEOF

Does this mean anything to anyone, other than the cURL setup is not working properly?

ipncheck.php produces the following:

IPNCHECK.PHP - Version 1.0

IPN TESTING - POSTING to PayPal via: ssl://www.paypal.com:443

IPN TESTING - Confirmation/Validation response: RESPONSE RECEIVED - Communications OKAY


Script finished.

...but ipn_test and ipn_test_return both return an illegal access message.

Managed to get ipncheck.php and curltest.php?paypal working just fine now.

So what's the score with ipn_test.php, then? - Presumably this is a test to see if information is passed back to my store correctly once a transaction has been completed, but without the customer actually needing to finish things off fully on their side, short of completing the transaction?

Well, I've checked the IPN Notification URL, currently set to:

https://mysite.tld/ipn_main_handler.php (where mysite.tld = the domain of my webstore - the cart is installed in the root directory of my website).

...and also the Return URL under Website Payment Preferences:

https://mysite.tld/index.php?main_page=checkout_process

...and I am pretty sure that there are no problems with either of those, so does anyone else know what might be causing ipn_test.php to die with an illegal access message?

After some further checking is

**https://mysite.tld/index.php?main_page=checkout_process
**
even necessary?

The above address is not a valid address for the cart, and Paypal does not require any kind of processing to be done through that address, so could it not be set as pretty much any address you like?

You have re-opened a discussion from 2007 about accessing the PayPal sandbox.
I'm not sure why you've done that (your post makes no reference to Sandbox), nor am I clear about what real "problem" you're talking about. Your CURL communications and IPN communications appear to be working fine.

coffee granules:

Using curltest with ?paypal parameter I am receiving the following error message:

ACK=Failure&L_ERRORCODE0=81002&L_SHORTMESSAGE0=Unspecified%20Method&L_LONGMESSAGE0=Method%20Specified%20is%20not%20Supported&L_SEVERITYCODE0=ErrorEOF

Does this mean anything to anyone, other than the cURL setup is not working properly?Actually, it means the CURL communication was successful. That error message comes from PayPal, and you would only see it if you were able to connect to them.

coffee granules:

ipncheck.php produces the following:

IPNCHECK.PHP - Version 1.0

IPN TESTING - POSTING to PayPal via: ssl://www.paypal.com:443

IPN TESTING - Confirmation/Validation response: RESPONSE RECEIVED - Communications OKAY

Script finished.

> **coffee granules:**
>
> ...but ipn_test and ipn_test_return both return an illegal access message.Good, because those are for developer-use only and shouldn't work for you anyway.

> **coffee granules:**
>
> does anyone else know what might be causing *ipn_test.php* to die with an **illegal access** message?That's by design. Ignore it.

> **coffee granules:**
>
> After some further checking is
> 
> **<https://mysite.tld/index.php?main_page=checkout_process>
> **
> even necessary?
> 
> The above address is not a valid address for the cart, and Paypal does not require any kind of processing to be done through that address, so could it not be set as pretty much any address you like?
The Auto-Return URL is used when the customer doesn't click the button to return to your site.  Zen Cart overrides that value with each transaction; however, you still need to give it a valid address or Paypal may disable the feature on you if it encounters failures. Same with the IPN URL.

Thanks for the reply, Doc, and my apologies for the incorrect posting. - I was trying to keep like subjects together.

Anyway, despite the successful returns from the tests, I am receiving emails from PayPal telling me:

Please check your server that handles PayPal Instant Payment Notifications (IPN). Instant Payment Notifications sent to the following URL(s) are failing:

https://mysite.tld/ipn_main_handler.php

I have verified that the file is present, have replaced it with a copy of the file from my original files, and have also tried

http://mysite.tld/ipn_main_handler.php

with no success.

The settings in PayPal have been checked several times, as have my settings in admin for the PayPal Express module, so I'm at a complete loss as to what is causing this.

I have even been through my files replacing files with originals where the existing files had been overwritten by contribution files and have also tried removing and reinstalling the PayPal module.

This is the https:// server log for my site and it looks like ipn_main_handler.php is working OK... so part of it is working fine and the rest (whatever is causing those error emails) I don't know...

66.211.170.66 - - [19/Nov/2008:00:32:45 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:46:31 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:50:41 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:50:52 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:51:15 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:51:58 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:53:20 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:01:56:02 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:01:25 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:12:07 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:14:27 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:23:23 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:25:35 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:33:28 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:02:38:16 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:16:11 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:23:02 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:23:14 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:23:35 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:24:18 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:25:40 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:28:22 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:33:42 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:44:23 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:03:50:58 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:04:04:37 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:04:06:04 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:04:41:33 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:04:48:19 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:04:48:49 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
216.113.191.33 - - [19/Nov/2008:05:17:40 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:05:19:37 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:06:14:09 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:06:46:38 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:06:56:00 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:06:59:43 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:06:59:56 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:00:18 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:01:01 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:02:23 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:05:04 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:10:26 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:21:08 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:32:14 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:42:30 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:44:04 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:07:47:48 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:08:23:07 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.231.188.64 - - [19/Nov/2008:08:24:39 -0800] "GET /robots.txt HTTP/1.1" 200 137 "-" "Gigabot/3.0 (http://www.gigablast.com/spider.html)"
66.231.188.64 - - [19/Nov/2008:08:24:44 -0800] "GET / HTTP/1.1" 200 9884 "-" "Gigabot/3.0 (http://www.gigablast.com/spider.html)"
66.211.170.66 - - [19/Nov/2008:08:25:18 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:08:43:57 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:08:48:58 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:08:54:14 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:08:58:15 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:02:25 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:05:58 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:11:10 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:12:42 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:14:24 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:15:42 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:28:04 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:32:39 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:33:49 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:34:01 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:34:24 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:35:05 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:36:27 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:39:10 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:44:33 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:45:50 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:46:02 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:46:23 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:47:07 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:48:29 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:50:39 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:51:13 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:55:16 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:09:56:36 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:07:18 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:16:39 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:28:42 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:29:18 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:33:11 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:48:47 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:10:59:21 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:11:05:38 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:11:11:23 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:11:22:13 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:11:55:25 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:11:55:31 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:11:59:30 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:12:24:41 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:12:27:34 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:12:36:44 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:12:41:19 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:01:43 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:01:54 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:02:15 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:02:58 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:04:20 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:07:03 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:09:11 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:12:25 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:13:34 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:23:09 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:13:44:31 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:00:55 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
79.74.239.23 - - [19/Nov/2008:14:01:35 -0800] "GET /ipn_main_handler.php HTTP/1.1" 200 65 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4"
79.74.239.23 - - [19/Nov/2008:14:01:37 -0800] "GET /favicon.ico HTTP/1.1" 200 22103 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4"
79.74.239.23 - - [19/Nov/2008:14:01:50 -0800] "GET /ipn_main_handler.php HTTP/1.1" 200 65 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4"
66.211.170.66 - - [19/Nov/2008:14:27:18 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:28:15 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:28:26 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:28:49 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:29:31 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:30:58 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:33:40 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"
66.211.170.66 - - [19/Nov/2008:14:39:04 -0800] "POST /ipn_main_handler.php HTTP/1.1" 403 610 "-" "-"

All those "403" numbers at the end of all the requests from 66.211.170.66 are "403 Forbidden" errors ... which are being generated by your server.
Perhaps your server's configuration doesn't like the requests from PayPal's server?

Yes, you are right. - I will need to speak to my webhost about this, because this should not be happening and I know that there is nothing that I personally have done to block PayPal.

Thanks again, Doc.

**[KEYWORDS] **paypal transaction won't work ipn_main_handler.php blocked 403 ipn no return [KEYWORDS] :P

OK, I've found a solution for people with the same problem as myself (basically blocked IPN requests from PayPal). It's not very nice and probably needs a rewritten Zen Cart module to fix it, but the solution (for me) was to add:

SecFilterEngine Off

to the root .htaccess file.

...and yes, this does turn mod_security off on your server...

Okay, thanks for posting the sledgehammer "fix" that's working for you.

However, forcing mod_security off is NOT a good solution for anybody, especially on your live store folder.

What would be a whole lot more helpful would be to get your host to indicate exactly which mod_security rule is being flagged in your case.

Using this information we can determine whether there's actually anything that can be done on the Zen Cart side, if anything. I'm not convinced it's a fault of Zen Cart, since a 403 directed at PayPal's server is responding to input coming directly from PayPal, not Zen Cart.

If the rule reveals something useful on the PayPal side, I'll see what I can get them to do about it, if anything.

... but I bet the 403 is a result of too-restrictive-rules on your host's part. But of course they'll deny that. They usually do. And they'll likely refuse to answer your request for more info in the name of protecting their security.