Why is my Apple Watch Series 8 not working even though it's charging?
Apple watch not working though the charge is flowing to apple watch
[Re-Titled by Moderator]
Apple Watch Series 8, watchOS 9
Did you already have a look at this related article?
If your Apple Watch won't charge or it won't turn on - Apple Support
Has the battery ever been replaced?
Have you been swimming with your watch?
The official Apple Support can diagnose the watch online, to find any issues: