Hi

This does not sound like an issue with Firefox but is something that the Apple support team should be able to help you with.

Hopefully you did not become a victim of a gift card scam where thieves steal stacks of gift cards from a store and and carefully get the information off of them and then go back to stores to put them back on racks. So when the card gets loaded up in store, the thieves when they find out it is loaded can then take the money off card before use.

Is It Even Possible to Avoid the Gift Card Scam? https://www.youtube.com/watch?v=x8-pzToSRSw