Following the most recent update, my Apple Watch Ultra 2 has stopped charging entirely, regardless of which charger I use. The screen displays an image of a charger accompanied by a red lightning bolt. Unfortunately, I am unable to perform a hard reset, as the device's battery is completely depleted.
Apple Watch Ultra 2, watchOS 11
Did you let your Apple Watch Ultra connected to the original Apple charging cable and an Apple 20w power adapter for at least 30min?
If the watch is still not starting up automatically, you should contact the official Apple Support about that.
Apple Watch Service and Repair - Apple Support
Also check this related article, if you haven't already:
If your Apple Watch won't charge or it won't turn on - Apple Support
Apple Watch Ultra 2 not charging after the last update
