PayPal account authentication settings are not yet set up

I have installed paypal express on zen cart 1.3.9.

When I click on the paypal button, I get this error message.

We are sorry for the inconvenience. The PayPal account authentication settings are not yet set up, or the API security information is incorrect. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002) 10002 Security error - Security header is not valid

I have read the help me files but have not anything on authentication settings.

I have tripled checked the API settings(user name, password, api password, signature, etc..) and they are correct.

I'm not sure what the authentication settings are?

Ok, I figured it out.
I had to unistall the paypal module and reinstall it with the correct API settings.
Thanks

Thanks for taking the time to follow up with your solution.

I am having the same problem but do not really understand how did you solve the problem.

I enter the correct user name, password, and signature. Could you provide more detail of your solution?

You must enter the correct API details, exactly as PayPal gives them to you.
And, use the Live site. Don't bother with sandbox.
Instructions here: https://www.zen-cart.com/getpaypal

If you're 1000% certain you've done that exactly, the report back with the EXACT error message YOU are getting.

http://www.zen-cart.com/forum/showthread.php?t=61199

I am having the exact same issue as the original poster along with the exact same message of "We are sorry for the inconvenience. The PayPal account authentication settings are not yet set up, or the API security information is incorrect. We are unable to complete your transaction. Please notify the store owner so they can correct this problem. (10002) 10002 Security error - Security header is not valid".

I've checked, checked and triple checked everything, to no avail.

zen version 1.5.4
paypal express module.
I've uninstalled and reinstalled it 3 times.

I've cut and paste and also manually input the api signature user name, password and code multiple times. I've checked these against the paypal setup but in fact have cut and paste them directly multiple times to no avail.
setup is live, not sandbox.
Ive enabled IPN and used the url specified in the zen module.
still getting the error, cannot figure out why at this point it is acting like it is the wrong ipn credentials.

There is some other pertinent information missing from the posting tips (information appearing above the text box when selecting reply to this message:
Has your site been upgraded? When? From what version(s)?
If you've upgraded, HOW did you upgrade? (official upgrade procedure or an automated script from your hosting company?)
What plugins/addons have you installed? When? If your problems are payment-related, what payment module(s) are you using? If it's shipping-related, which shipping module(s) are you using?

This is a new, manual installation (not a "one-click" install such as provided by a hosting company). No plugins or addons have been installed. The only payment module activated is the one with the issue, paypal express which is why I am surprised it is not working right out of the gate considering I have meticulously made certain the api credentials are exactly as provided by paypal.

1. Turn on PayPal Debug Logging ... http://www.zen-cart.com/showthread.php?61199-Debug-Logging-PayPal
2. Attempt to pay with PayPal, so that it triggers the error.
3. Look in the /logs folder to get the PayPal debug CURL log that was generated. Be sure that it shows the error in the Response section
4. Report the error to PayPal via https://www.paypal.com/mts and include the text from that log file.

The PayPal technicians can look into their details using the transaction-attempt info from that log along with your account credentials as contained in the log, to determine what may be wrong with your account on their end.

Thanks everyone for the response. I appreciate the attention given sorry for wasting anyones time.
The solution has been found and once again proves the adage that 98% of all computer problems are operator related. After going round and round (the client swore they cut and pasted the credentials directly from Paypal - TWICE) I finally had them send me a screenshot of the credential page in paypal. the api signature given to me was along the lines of xxxx_api.something.com. And it really did look like a cut and paste to me. However, when I got the screenshot the api signature was xxxx_api1.something.com. Note a numeral 1 magically appeared. Now it works of course having the right credentials. In the future I might require a screenshot. Lesson learned.

I recently upgraded to 1.5.4. I paid my web host $250 to do this. I have had non stop trouble with paypal since then and ma losing business left and right. I have been on the phone several times with paypal and they cannot fix whatever is wrong. They had me delete 2 modules and then go to paypal standard. That is now giving my customers an error message that I am not taking orders from their region. I think it is a big with the upgrade.
Totally frustrated and looking at Shopify or an entire new cart somewhere else.
Paula

Paulad:

I recently upgraded to 1.5.4. I paid my web host $250 to do this. I have had non stop trouble with paypal since then and ma losing business left and right. I have been on the phone several times with paypal and they cannot fix whatever is wrong. They had me delete 2 modules and then go to paypal standard. That is now giving my customers an error message that I am not taking orders from their region. I think it is a big with the upgrade.
Totally frustrated and looking at Shopify or an entire new cart somewhere else.
Paula

My feeling is that the host is to blame not ZC, and well, for anyone to help more information is needed than "have issues". If by looking for a cart somewhere else you mean with a different host? I'd probably agree... They should be fixing the issue since it seems (without further information) that they caused it...

Tonight the guy in charge spent a lot of time on it whic I really appreciate. Right now it is working again. Hopefully this is the end of it. I am on an Apple and I think part of the problem was Apple filling in things for me when I redid the IPN stuff. Bad move after 40 years on a p.c. And I do know that some of the time paypal was offline. But Geez webcarts really shouldn't be this difficult! Paula