Hi f41e654996ab2438,
Sorry to hear all of your Battlefield 6 progress and unlocks appear to be gone after returning to the game. I understand how concerning it is to suddenly see your account back at Rank 1.
Battlefield 6 progress is stored through your EA Account, so please first make sure your Xbox account is still linked to the same EA Account you previously used to play.
You can check your linked accounts here: Battlefield 6 account linking and access guide
Please avoid unlinking or relinking any accounts for now, as making account-linking changes could make the situation more complicated.
Thanks for your patience, and I hope we can narrow down what happened.