Before you start doing manual work, we have seen several slide problems crop up here that can be easily fixed.
First of all, do you hear any sound from the motors? If the motors are working okay, there can be problems with the track or motors themselves. If the motors make a sound, but the slide doesn't move, you probably have a voltage problem.
Next, what is your battery voltage. I have the full length slide and if my batteries are lower than 12.2v, there is no way to move the slide. I have had this particular problem a couple of times. My solution was to take a regular 120v battery charger, run the generator, and boost up the batteries.
Another option is to locate the slide controller. There is a method of overriding the slide controller and you can open, or close, the slide. There are several videos on YouTube about this. Here is one: