Paypal Standard problem - orders stuck in pending

[colmagee]

Hi,

Lately I have had a problem with standard Paypal payments on Joomla 2.5.28  / VirtueMart 2.6.22 (yes I know these are very old versions but  I just haven't had time to undertake the massive task of upgrading the website to the latest versions).
This was working fine a couple of months ago but just recently it has come to light that it has stopped working despite me not changing anything.

After successful payment from Paypal this is returning to a blank page, eg:
http://www.barandkitchen.com/index.php?option=com_virtuemart&view=pluginresponse&task=pluginresponsereceived&on=ZL8R0147&pm=4&Itemid=129&lang=

The order status is stuck as 'pending' and the Paypal log file is logging this information, eg:

"2018-08-06 11:00:39 ERROR validateIpnContent: Invalid IPN validation: NO ANSWER FROM PAYPAL"

I have spoken to Paypal and they have provided the following response -

Just to clarify IPN is the only way PayPal updates your eCommerce's backend. This functionality is active a working on your account.
So, we have sent the IPN correctly and we got a HTTP 200 OK response but your server didn't make the postback correctly. This process is done by your IPN listener script, here are the steps: (IPN authentication)
DONE by PayPal
1) PayPal sends an IPN message via POST HTTP to your server
2) Your listeners responds with a 200 http OK
Done by your Script (we cannot access this process)
3) Your listener sends to PayPal via POST the IPN message unaltered with the same information and the same order and preceded by cmd=_notify-validate
4) PayPal restores "VERIFIED" if the message corresponds to the one that we sent or "INVALID" if it isn't the same.

I have to admit I don't actually understand what this means or how to fix it. Can anyone help please? If it's possible that some files have become corrupt or become 'out of sync' could I restore some of the core Joomla files to try and fix the issue ?

Thanks a lot

[GJC Web Design]

hmmm

it returns a proper 200 to Paypal  but then the verify is failing


if u look at plugins\vmpayment\paypal\paypal\helpers\paypal.php vm2.6 around lines 718 to start debugging this