Or it could simply be dust or something in the motor which prevents it from vibrating (had that from day 1 - fixed it by leaving the motor running overnight).
You could try to run the motor at 255 (highest speed) and it might grind () the dust, if it is dust, as root, run: (don't touch the screen/keys after running the command - till the vibra works)
I don't know the specs of the motor and how long it could run for, but if/when the motor works touch any key to stop it (or the screen)