We've not had the issue but this may help, the attached doc includes an electrical diagram on page 19 of the rack and pinion slide. as you see the electrical power goes from the battery through one of the reset circuit breakers in the front storage compartment, then through the switch to the motor. Which one of the reset breakers I don't know but I think one with a big white with red striped wire. There is no fuse per say just the reset breaker which is the "fuse". Here is a pic of our reset breakers in the front storage compartment.
If the problem is a mechanical, The attached doc also includes the mechanical portion of the rack and pinion slide. Seems to me that if the slide moves while using the mechanical override, then I would think that the motor is connected to the gear mechanism and it's not jammed up. Not sure how the geared mechanism works inside of the clutch mechanism.
I would start troubleshooting power, If 12VDC power is coming from the battery through the reset breaker, through the switch then out to the rack motor then it should at least turn the motor. What would be left then would be mechanical, motor physical connection to the rack gear mechanism.