Himar227 wrote:
I did, they could not tell what happened.
I can tell you exactly what happened. The battery was left fully discharged for an extended period of time and is now unable to accept enough power to reboot your Apple Watch. Operator Error!
Your signature mentions Apple Watch Ultra, which should be capable of fast (high power) charging. Your only hope is to use the original Apple fast charge USB-C charger cable supplied with the watch, attached to the highest rated Apple USB-C power adaptor you have available. Ideally that will be at least a 30W or even a 70W adaptor. Leave it overnight and hope it can get enough charge to restart.
Even if you get it to restart now the battery is likely to be damaged by being deep discharged. You will need to have your Apple Watch overhauled by Apple, and probably request a battery replacement.