Series 6 Watch makes charging sound but screen will not turn on
My apple watch makes the sound when I put it on the charger but the screen stays black and I cannot force restart it.
Apple Watch Series 6, watchOS 7
Perhaps this article will help:
If your Apple Watch won't charge or it won't turn on - Apple Support
Also make sure you don't have Screen Curtain enabled. See the 'Use Screen Curtain on your Apple Watch' section in:
If you still need help, contact Apple Support.