Attempt to charge the watch for an extended period to ascertain if the issues persist.
If the issues persist, attempt to force restart the watch.
Press and hold both the side button and the Digital Crown simultaneously until the screen turns black and the Apple logo reappears. Release both buttons. Your watch may take a few moments to restart.
Please refrain from performing this action when updating watchOS.
It is possible that your watch has sustained severe hardware damage and requires replacement. However, by implementing these troubleshooting steps, you have exhausted the available solutions you can try yourself.