OK - I'm nearly there, my upgrade to 8.6 is working (on testing server) And I've established that PayPal is working. So now, I suppose this is a general question rather than an upgrade help question.
When on the PayPal site and a user presses "Cancel and return to [your business or club]" At the moment, all the user sees when the return completes is a message saying "[Website url] says Process Failed". Which is a bit unhelpful as far as end users are concerned. Is there a way to change this to something more meaningful such as "Ooops something went wrong. Your payment has not been processed.
I have searched the fora but nothing comes up for search terms change process failed message