If a user contacts your school because of an error they received that their payment on a form (Registration, Giving, or Application), we can access the failed payment record to see what may have caused the issue.
We can find the failed payment through onMessage > Approval > Giving >
Mark the show failed check box
Click on the name of the user whose payment failed
Here it shows the payment failed, and will display a code.
Note: This error code comes from the Payment Gateway, so you need to contact them to determine the reason teh transaction failed.