If your MP Rotator nozzle is not rotating, the MP Rotator may have some debris in the nozzle. Remove the nozzle to inspect and clean the filter screen. Replace the nozzle and turn the valve on to run sprinklers. Increase the radius to its largest radius adjustment by turning the center screw 4 full turns counter clockwise. Then adjust the arc adjustment ring to its largest arc by turning it clockwise. You may have to open and close the arc adjustment several times to pass the debris.
Also, MP Rotators rely upon the incoming pressure of the water passing through the nozzle to produce rotation of the top portion of the nozzle. If this pressure is restricted, it can result in slow rotation or no rotation at all. The MP Rotators perform optimally at 40 PSI. Take a pressure reading at the head with an MP Gauge to ensure there is a sufficient pressure supply. Also, using a Pro-Spray PRS40 can help dial the pressure in to its optimal level.