If the slide is currently closed or partially closed, the first thing I would do is pull the bulb seal back from the top of wall and inspect the wiring coming out of the top of the motor. Make sure the six wires coming out of the motor are not damaged and make sure the encoder on the top of the motor (under the plastic cover) has not been damaged.
When operating my full-wall slide, I could watch the tremendous torque cause the motor to move because the motor is held down my a very small setscrew. That set screw can come loose, bend or even shear off and then the motor can move and pinch a wire or even damage the encoder.
You should also check to make sure the harness connecting the motor to the Controller is plugged in securely.
One troubleshooting step you can try is to see if the manual override procedure will work (see below). This will verify that both motors are turning properly and allow you to operate the slide if both motors are operational and a key wire is not completely broken.
If you are able to retract and extend the slide this way, try going through the resync procedure again.
Make sure there is nothing obstructing the movement of the slide and be sure to hold the Extend / Retract button for 2 - 3 seconds after the slide is fully extended or retracted to keep the motors in sync.
I had the crappy Schwintek Slide Mechanism replaced with the Vroom Slide System, which is far superior in terms of design and components. The Schwintek Slide Mechanism is just not robust enough for a heavy, full-wall slide. One of the weakest links is the motor is not bolted down into the bearing block. The motor housing is kept from spinning by four pins and it is only held down by a single small setscrew. Over time the motor starts moving more and more from the tremendous torque and it can pinch a wire or start lifting out of the bearing block (popping sound while moving).
__________________
|