ATV4 does not turn on/off CEC beamer (BENQ W1070)

Hi have two ATV4, one on my Samsung TV and one on my new BENQ W1070 beamer. With the TV, the CEC functionality to control volume and turn the TV on and off with the ATV4 remote works perfectly. With the beamer, I only could manually teach the ATV4 remote to control volume by IR. The functionality to set the ATV4 remote to turn on/off home theatre in 'Settings' is disabled.

In the beamer setup, CEC is 'on' for HDMI.

1. Why does CEC not work with the BENQ Beamer? Is this an ATV4 or BENQ issue?

2. Why can't I manually teach the ATV4 remote via IR?

3. Is there a solution?