the motors give red light and then it suddenly stops can i know the reason ?
If the light goes out, that usually indicates a problem with the motor, port, or cable.
Please check out the articles on Help.Vex.com they are very informative for the V5 system.
If the red light is constant, then the motor is working fine, but generally if the motor blinks then what might have happened is known as ESD or electrostatic discharge. This is very well known to blow out ports and motors.
Yea @ItsMe is correct. ESD has been a bad problem for a while and has show a lot more this year because of all the rubbing of the cubes when they go up trays and things.