Authorize.net Error Code 54
This error code from Authorize.net means the transaction does not meet the criteria for issuing a credit. This could be for several reasons. If it's an ACH refund test in your Sandbox then it could be that the ACH transaction is simulated and not a real transaction.
If you are trying to apply a refund or partial refund from your Production Org it could be one of the following:
Authorize.net suggests that you consider applying for Expanded Credit-Return Capabilities if the merchant needs to refund transactions older than 120 days.
- The transaction hasn't yet settled and needs to be voided.
- The transaction has settled more than 120 days ago.