Hi @alfeeauyeung, could you please go to the Bluetooth settings, and Unpair your remote. Then, please pair it again. Instructions: How to pair the AirMote?
If this also doesn’t work, please check whether you can pair the AirMote to another device like your laptop, phone or tablet. This will help us identify whether the remote is faulty or not. I trust that you already swapped out the batteries just to be sure.
Finally, if the remote works on another device, but unpairing and re-pairing doesn’t work on the projector, please perform a factory reset as a last resort. Let us know if these suggestions resolved your issue.