I know you have tried it without the switch, which is good to remove any possible outside causes. However, did you check to see that you have connected the wires properly to the motor. You must connect the receiver to a specific connector, and the LNB to a specific connector. I would imagine that if they are reversed, the motor will not move, but the IF signal may still pass through.
Just a thought.
Also, are you sure you have the various satellites set for USALS in the receiver's sat setup menu? If you recently did a reset, or loaded up a new channel list, you may have lost satellite motor position settings. In that case, the motor will not move automatically from bird to bird.