If you are using V8.1.0.1 to V8.1.0.5, and if you have the error on PayFlow Link or PayPal Payment Advanced after return from PayPal, Please do the following changes:
1. Open paypalpflinkresult.asp
2. Replace all "PError" (without double quote) to PauthCode
3. Save the file and upload to your site.
4. Open paypalpymtresult.asp
5. Replace all "PError" (without double quote) to PauthCode
6. Save the file and upload to your site.