[sanddrag]

Originally Posted by Max Lobovsky

A single solenoid will always move the cylinder to one or the other position. When the robot is disabled, the solenoid will always be in its off position, and the cylinder will consequently always be in the same position. If you would like the piston to be in the other position when the robot is disabled, you need to switch the hoses going to the two ends of the cylinder.

Just to speak a little further on this:
The solenoid "defaults" to a position when no current is applied and switches positions when current is applied. When your robot is disabled, no current is applied so if goes to whatever the default is. When you turn the robot on and it uis extending or whatever, then in your program or on the relay, you need to see if current is being applied to the solenoid. If so, don't have it do that. Or if not, do apply current (switch the relay on) Or, swap the hoses. Doing one of those things should reverse the action to get the desired effect.

Or just replace the unit with a double solenoid so you have total control over it.