You need to get a volt meter and check for voltage at the motor when someone activates the switch.
If no voltage present then check for 12V at the back of the switch.
If present then check for voltage at the other end of the switch when its depressed.
If there's no voltage anywhere then I would try to trace the feed wire (for the switch) back to the converter or in some cases, directly to the battery.
This all assumes the slide is electric and not hydraulic. If hyd then check the switch and the wiring at the pump for voltage and perform the same tracing back to its power source.