Microsoft does reference CEC (Consumer Electronic Control) on their Microsoft Teams Room documentation, that it has put out and you can find that blurb here. A consumer TV used as a front of room display needs to support/enable the Consumer Electronics Control (CEC) feature of HDMI so that it can switch automatically to an active video source
After buying new 8K cables, the issue continued. After a lot of trial and error, I made my Vizio soundbar eArc work by 1. making sure I was using HDMI port #2 for the soundbar; 2. updating the soundbar firmware (eArc responsiveness was a listed issue in the update) and finally 3. Powering everything off and on again.. 26 219 84 100 356 176 477 422