Hey , they are a few possibilities of what it could be, the simplest is over time the seals etc wear out and the glass might just have to be readjusted to sit flush again, the second is that the cables have stretched over time and aren't driving the sliding mechs all the way forward, these are the 2 simplest and most likely i think,I doubt the motor is gone as when the go they just simply stop working. Best bet would be to find a sunroof place nearby and pop in ,most deal in aftermarket roofs but usually have somebody skilled in repairing factory ones. I'm not sure what state your in but I'd be happy to try and point you in the right direction.