I have an MSO-compatible device..
Microsft Office?
What is an MSO-compatible device, google is not helping...
On the PC side:
What kind of video card are you using? Intel/AMD integrated graphics? A separate GPU? Model?
While it could be handy on a PC, I have yet to see any that supports CEC - apart, as said, the RPi*.
If you have a RPi, why not check whether you are getting CEC events from the display? I'm pretty sure you'll find none, since:
It makes almost no sense for a monitor to support CEC, as the functions are usually accessed from a remote, and that Acer does not have one.
Its manual only mention CEC in the pinout of the HDMI (but that's just the standard pinout).
On a completely different side (maybe one side of the PC):
A colleague of mine has got a new, fancy mouse. He was fading in and out of our Teams call until he realized he has a scroll wheel on the side of the mouse, and it controls the audio system!
* You can use cec-client.