I was able to access the rewards program for Xbox on the mobile app until today. Now that part of the app is completely gone. I can still see my points in the Rewards Hub and can do online via PC things to earn points but the interaction in the mobile and PC Xbox apps no longer show quests, etc.
I did have a US based account that didn't expire until today but had transferred everything to New Zealand (where I now live) and have a paid New Zealand Game Pass Ultimate subscription until 2-26-2026. This is the only thing I can think of that has changed.
I have signed out of the Xbox mobile app and uninstalled and re-installed it to no avail. Just lost as to why the functionality of the app would literally disappear overnight.