@Mina ,
First I would check for any obstructions in the motors and that the motors are making proper contact with the CoDrone board. This video goes over troubleshooting the motors. If it's still veering to the left, it may be that one of your motors on the left side is a bit slower. Try swapping a motor from the left to the right side. Make sure you keep the proper propeller orientation! The LED not lighting up may be due to a crash.