Happened to one of our slides earlier this year. For us, one of the motors died (or they said something possibly of coiled up). Motor was replaced under extended warranty and works good now...I suggest watching some youtube videos on them...we learned some things after the fact. You can do a by pass and if the motor is not broke, you can get it to retract. Also learned to not stop the slide in the middle of it going out or in. You amy also need to run the slide in and out 3 times to get it to reset. That is after you can get it moving...
Also, find the slide controller. There should be a way written on it about getting a code from it, it will tell you what the problem is.