Hi William,
I am curious if you have been able to fix it? I have exact the same issue. My son left his bike with a one day old bafang middrive BBS01 out in the rain.....
next morning it would not drive. The battery and the lcd screen and headlight are working, but not the motor.
I opened the controller of the motor, but it was completely dry, and also all the connecters, I took them apart and put them in a bag of rice for five days. So they are dry to.
But now I assume for some reason the motor is not getting any electric current...
I am curious if you were able to fix yours?
Kind regards Fredric