No Paypal orders are working now

I have the latest version of zencart set up.
I am using site ground as a host.
Since last thursday none of my paypal orders are going through.
I am getting notice from paypal but zencart is not recording the order.
I have not installed anything new the only thing I have done is try and reset up
paypal.
I am having to contact the customer and send the order manually
which I don't want to do and is the whole reason I set up zen cart to begin with.
Can some one in simple terms help me.
WW.

I just ran the curl test and that worked and every other bit of info I can find.
Please I could really use some help on this.
WW

Have you checked your setting in your PayPal Account admin?

windwoman:

Since last thursday none of my paypal orders are going through.
What's special about "last thursday"?
Any changes to your software?
Do any upgrades?
Install anything new?
Did your hosting company upgrade anything?
Did your hosting company change anything in their network or firewall?
Did you receive any emails from PayPal about IPN failures?
Is your "Instant Payment Notifications" option still enabled in your PayPal account profile on the PayPal website?

windwoman:

the only thing I have done is try and reset up
paypal.
What exactly do you mean by that?
Why did you try to do that?
Was this before or after you started having problems?

windwoman:

I just followed all the instructions for checking the paypal set up.
The instructions include a recommendation to turn on debug logging and collect log files from the PayPal transactions happening on your store. What's in those logs? Please zip them and post them here for analysis.

What's special about "last thursday"?
Any changes to your software?
Do any upgrades?
Install anything new?
Did your hosting company upgrade anything?
Did your hosting company change anything in their network or firewall?
Did you receive any emails from PayPal about IPN failures?
Is your "Instant Payment Notifications" option still enabled in your PayPal account profile on the PayPal website?

I changed my merchant account but the gateway is the same company
I did not do an upgrade that was done about June to the latest version.
Nothing new installed

Not sure on the hosting company I will ask in the morning.
Nothing from Paypal about IPN Failures. I am getting the normal notice that a payment has been made.
And the IPN is enables and the url address are correct.
I did test an order and Paypal returned me to the website but no order was recorded on zen cart at all.

What exactly do you mean by that?
Why did you try to do that?
Was this before or after you started having problems?

I went and made sure that the IPN was set up correct and that the url addresses were correct.
I also turned on the Debugging program
I did this today after having problems

I zipped the logs and I hope attached them to this latest note.
Thanks
WW

If you're using PayPal Website Payments Standard, the logs show no response from PayPal's servers. This means the IPNs are not getting through your host's firewall, or maybe you've got some software on your site blocking the IPNs from getting through ... perhaps some sort of SEO or mod_rewrite package.

Your logs contain attempts to use Express Checkout, but show an error message "Security header is not valid" ... which occurs when you attempt to use Express Checkout without configuring the API security credentials correctly.