"Paypal payment notification refused" issue

-- HikaShop version -- : 2.3.5
-- Joomla version -- : 3.3.6

We are having a problem with purchases through from the Paypal Sandbox with an email being sent after a purchase is complete with the subject heading:

Paypal payment notification refused:invalid response

This is the process we are seeing:

1) Item added to cart
2) Checkout and click Finish to pay via Paypal
3) Redirects to Paypal (Sandbox) and requests Test Buyer login
4) After Login, option to Pay Now which is clicked.
5) Paypal (Sandbox) shows the payment has completed successfully.
6) Email received with subject heading "Paypal payment notification refused:invalid response" with the body listing the order number.

Checking the Paypal Sandbox buyer and seller accounts it shows the transactions both out and in have processed correctly.

I have checked this page: www.hikashop.com/index.php?option=com_up...rror#invalidresponse

and therefore I have also checked the Paypal IPs being used and they are valid so that does not appear to be the issue, but something is causing this.

Please can you advise. Thanks in advance.

Hello,
Please look at the thread below, that should help you solve the problem:
www.hikashop.com/en/support/forum/4-how-...s-stays-created.html

If not, can you show me how did you configured your Paypal payment method through some screenshots ?

Thanks Mohamed. I have had a look at that thread. It suggests enabling the Debug mode which I have done and generated a log file. Like the other thread it says I have [charset] => windows-1252 but like the other poster I haven't changed anything in the site. Could that be the problem? I had a look on the Paypal dev site you linked to, but couldn't see anything about encoding on there.

The end of the log file shows:

HTTP/1.0 302 Found
Location: https://www.sandbox.paypal.com
Server: BigIP
Connection: close
Content-Length: 0

invalid response

Hi Mohammed, not sure where to email as we have the business package, but are we able to send you the log file for this Paypal issue?

Thanks Nicolas for taking a look at this. We have now found the cause of the problem and it was caused by missing off the 's' in the https for the Paypal Sandbox URL. Easily missed, but obviously critical!