Can’t update my Apple Watch
why I can’t update my Apple Watch while I’m charging it and it was above 50%?
Question marked as
What series watch is it? Any error messages, etc.?
FWIW, a lot of people have problems updating a series 3 watch due to insufficient memory. in some cases, unpairing the watch, completely erasing it, and then updating and restoring the backup will allow you to update it.
Unpair and erase your Apple Watch - Apple Support
Another option (maybe even better, if possible) is to take to make an appointment at the Genius Bar in an Apple Store near you and let them update it.
Genius Bar Reservation and Apple Support Options - Apple