The first thing that I would do is to disconnect the brake lever switch connector from the controller and see if it runs then. Sometimes brake lever switches become defective and lock into the on position which tells the controller to turn the motor off. If the bike works when the brake switch is disconnected from the controller then the bike needs a new brake lever.
If it does not run after disconnecting the brake switch let me know and we will take it from there.
Kris william