I was programming my arm and realized that it is two heavy for two motors. So we decided to add 2 more motors and connect the 2 motors on the left side with 1 y-cable and the 2 motors on the other side with another y-cable. But after we did this the motors stopped working completely. They are not even moving.
I can’t think of a motor distribution in which the two left side motors spin in the same direction. My guess is it’s not moving because the two left motors need to spin in opposite directions. Just switch the leads of the wire on either both bottom motors (left and right) or both top motors to be black-to-red instead of black-to-black, and they should spin in the opposite direction. Good luck!