Sounds like maybe something has come loose or a wire has broken into. You can check and see if you can find a break? You could also take a 12 volt battery out to the actuator and see if it will move? If it moves, it's not the actuator. If it doesn't move, the actuator is probably bad? These are a couple of things you should be able to check yourself? Good Luck!
Take a voltmeter and see if your getting a voltage for a second or so across M1 & 2 terminals when you tell it to move. If so you may want to try a master reset of the 4DTV this sometimes solves the problem. I know some MOV's also go in the 4DTV that will cause this problem.