HDMI CEC Sleep with Yealink A20 meeting bar

We are setting up a bunch of Yealink A20 meeting bars and the idle-timeout setting in the Zoom Rooms back end does not seem to be working. This is meant to dim the touch screen and turn the TV off after a specified time of inactivity.

Does anyone have any experience with this?

Is there a solution others are using other than turning the TVs in the meeting rooms on and off with the TV remote manually?

Yealink say it is a Zoom issue, as they only build hardware.

Regards,

Martin