What to do to get it back in sync?
Have you already tried to connect the controller with a cable and to update the controller?
Do you mean to connect the Konttoler with the cable to the xbox on the side? Nope haven't yet. I tried another method yesterday, it didn't work and then I didn't feel like trying any more.
Yes exactly. And in the settings under accessories, I think you can update the controller. Has worked for me before