Please follow below steps for troubleshooting:
(1) Check if the remote receiver is turned off by accident in OSD. It should be turned to Front/Top/Front+Top.
(2) Check if the batteries are out of power. Replace both of the batteries with new ones.
(3) Make sure you are not too far away from the projector. Stand within 7 meters from the projector.
(4) Remove the obstacles between the remote control and projector.