Quote Originally Posted by imen View Post
In the last couple of days, paypal express checkout is not working properly. Final check out page turns blank.

I notice the paypal express checkout page format has changed. Is there recent change on the paypal end that may have effected my zencart version?

I also restored the data base prior to the last transaction, that didn't fix the problem unfortunately.

What could be the problem? Where should I begin to debug?

Thanks!
Check your payPal settings regarding returning to the store after purchase and ipn handling. And then compare those settings with information in your Zen Cart setup, to be sure that things line up. Also be sure that any paths from payPal are directed at your current zC setup, not a previous one.