Please do the following:
-Check that the motors are in the correct position and that the motors are connected with their ends in the following pattern:
Motor 1(M1) should be on the left side (Red Black)
Motor 2(M2) should be on the right side(Black Red)

There should be little plus and minus indicators to show this (red is positive "+", black is negative"-")

If this does not work can you please provide a picture of your setup if possible videos work well too!