Paypal Payment Confirmation Error

Hi,

I was successfully able to integrate HikaSerial with HikaShop and its working fine for several payment methods, such as Stripe, with payments being set to 'confirmed' and emails being sent with the serials successfully. However there seems to be an issue with either HikaSerial or Hikashop when handling Paypal payment notifications.

I followed all the instructions from the following page and still Paypal payments are not being set to confirmed, even though I can see the transactions when I log into my Paypal Account:
www.hikashop.com/support/documentation/i...or.html#notification

I enabled Debug mode but payment logs are empty but I receive the following notification from HikaSerial/shop:
Hello,
A Paypal notification was refused because the connection to the confirmation server failed.

Check the documentation concerning this issue at www.hikashop.com/index.php?option=com_up...pal-error#connection
This notification was for the order B4X3 on the website edi-manager.com/ You can access the order details directly by clicking on the link below after logging in your back end:
edi-manager.com/administrator/index.php?...ask=edit&order_id=43

Since Stripe is working fine, obviously there isnt any issues on my webserver side, so I assume its either something related to Hikashop or Paypal itself.

Can you please shed some light here?

Thanks in advance
Marco