Topic: PayPal error: This site is using an incorrect PayPal certificate!
If you are getting this error message when trying to pay with PayPal Express Checkout or Direct Payment then you will need to update your PayPal SDK files. A new version is available as a free download here: http://www.ashopsoftware.com/dlcounter
Unpack the PayPal SDK files to your harddrive and then upload them to your AShop installation, overwriting the current files, to fix the problem.