What happened to my $80 Apple Gift Card?

Without further information, it's impossible for anyone here to even guess as to what you mean. Please post back and explain fully what your situation is and what help you would like from us, who are all just fellow users.

Regards.

The question you pose isn't clear so I'm going to work with the assumption that you loaded a gift card but your $80 isn't showing up on a certain device. If you loaded funds onto an up to date device but tried to access them on an out of date device, there seems to be some issue that causes a desynchronization of account balance. I would suggest making sure your device is up to date, but considering iOS 18 I would also create a backup of that device first just in case an important note gets broken.