What's the Store Experience Activity

I'm sorry that you had a bad experience, unfortunately it seems that you bought an already changed code, with the prepaid cards the mynosrist stores are in charge of activating the cards so it is possible that they did not activate it in the store (it
is a measure to avoid thefts, so when you pay the card they activate it, the manager may not)

This sounds like the store you bought it from, didn't activate it. Take the card, with receipt back to the store, explain what is happening and get them to activate it.

Are you trying this from a computer or console, try different browsers and make sure you account security is up to date.

All xbox ones recieved a console update recently so its probably regarding that

Yes, it is an official update.