Over the range microwave turntable motors often fail due to normal in home use, when this happen the glass turn table will stop turning. Replacing a microwave turntable is relatively simple, Philips screw driver will handle most of the job.
By removing the bottom panel of the over the range microwave you will gain access to the turntable motor. The screws along the bottom edge removed will allow the bottom to swing down and out of the way.
With the bottom panel swung down the turntable motor is visible, removing the one mount screw and twisting will release the motor. Unplug the wires and reinstall on the new motor. Button the bottom panel back up before making any test.
Place a bowl or cup on the turntable and run a test cycle the glass table should rotate. Check your use and care manual regarding the weight limit of the motor.