I'm having difficulties obtaining a refund after the credit card expired. The merchant is willing to provide a refund, but Authorize.net doesn't allow it. After a conference call with the merchant and Authorize.net support, it turns out the merchant needs to add Expanded Credit Capabilities to their account. That service is free, but it involves filling out a form and that makes the merchant a bit reluctant.
This is happening even though the transaction was less than a month ago, the same credit card account is still active, and the new card has the same number. The merchant tried just updating the expiration date, but that didn't work.