Lost two prime aerial flying days from this simple error.
Hope this remedy saves you.
Short version: USB Cable broke internally. Get new cable.
And watch for notice/window popup asking "DJI Accessory" needs to connect.
Long Version:
So planned...
They can go from debris or water in the motor too. Me personally, I would put props on and make sure they spin freely, then try again with DJI Assistant 2. If you still get the ESC error, it's probably time for a trip to the service department...