Apple watch

There is a good chance this is a software glitch which will be resolved by julieda’s restart suggestion. If the problem persists please check your charging accessories and if possible test with a different power adapter and magnetic cable. Then see If your Apple Watch won't charge or it won't turn on - Apple Support

Make sure you have the latest updates on your iPhone and Watch. Next, reset your Watch by pressing in the crown and side button until you see the Apple logo. then release both.

New charger? Did you find and remove all the protective plastic film around the magnetic head? Certainly test with a different USB power adapter, the one you use for your iPhone will be ideal.