Are you using a single solenoid valve? Those switch to their default position if they don’t receive the signal to go to a different one. Thus, when you hit the disable button the solenoid flips to the default position, which makes the arms move, and then you can’t switch them back because the robot is in disabled mode.
Try using double solenoid valves instead, those will hold their last position if they are given no signal.
The SMC solenoids you received in the kit are double solenoids. If you use those, you’ll be set. They need to be assembled, but that is fairly simple. The air from your pneumatic system goes into the middle inlet on the side with three openings, and the two sides of the cylinder go to the outlets on the side with two holes. The pneumatics manual will explain it better than I can.