John inside the cabinet behind the locking arm you'll find a plastic covering. Remove it and it will reveal the locking arm. (You'll need a square nut driver) Make sure nothing is restricting it. Check for power to the arm. There is a sensor that determines when the arm is fully unlocked. If it does not sense this the slide motor will not operate.
Best of luck, Keep us posted and Happy Trails!!!
Tony & Ruth........... FMCA#F416727
Newmar Dutch Star 4320, Spartan MM Chassis, Cat C9, Jeep Grand Cherokee,with Hemi, hooked up with a Blue Ox Aventa LX, and Brake Buddy.