Please follow the steps to fix the issue.
Step 1
Please press the Voice Search button on the remote to check that it is connected to the BenQ QS02.
Step 2
If your remote is not connected to the BenQ QS02, please restart your projector to enter the Bluetooth pairing process, and go to Step 3 if your remote successfully connects to the BenQ QS02 after rebooting.
Step 3
Press and hold the Play/Pause button on your remote if your remote is connected to the BenQ QS02.
Step 4
Then, press the Navigation and OK buttons to go to Settings > Device Preference > Display & Sound > HDMI CEC > CEC, and turn on CEC if it isn't enabled already. Restart your projector to complete the process.