Gift code not working

I have a $5 gift code from xbox that says it is redeemable by 8/31/2020, so today should be the last day to redeem it, however I keep getting a message saying it is expired. Having spoken to tech via web chat and phone they confirm the code is still valid,
but were unable to resolve the issue and declined to send me a new code, infact the tech I spoke to over the phone disconnected the call after having me wait on the line for over 30 minutes!

:)