Ive literally had this same thing happen to me with my GT. I updated my board to the latest firmware (like an idiot) and picked the board up and engaged the motor with my hands forward then backwards. Then my motor came to a stop and there was no signs of life after that. Ive left it plugged into the charger for days with no response from the app. No error codes or nothing. The board doesn't even show up also no power to the board. I took the board completely apart insuring not to remove the BMS cable for the controller and inspected the inside of the controller box. As I push the power button you can hear a tiny faint beep from the controller but nothing happens after that. I really miss riding this damn board. Ive been borrowing my buddies XR to scratch my itch in while I wait for some solid answers because FM just wants me to send it in and it's out of warranty so screw that.