Long shot possibly but have you verified your charger is still properly working? Could you try somebody else's charger (if you have access) that is known to work. Or try your charger on somebody else's watch that is compatible with it to see if it still works.

Sometimes cables and chargers just go bad. For a while I thought my TV was slowly dying because the it would randomly have issues with an HDMI port. Turns out the TV is fine and one my more expensive cables with a more robust cover (hard to bend to protect it) went bad. Cable was over 10 years old though. But my other ones bought at the same time (same ones) are fine.