You need to press the option and F3 to switch your Macbook to the projection mode if you use cable connection.
1. HDMI Connection
First, connect the MacBook to the projector via HDMI.
2. Switch the signal source
Then switch the projector's signal source to
HDMI input
3. Switch the mode
Finally, press the
option and
F3 keys on the keyboard of your MacBook to switch to the projection mode.