I just updated my Mac’s OS from Catalina to Monterey 12.3. My LG monitor is no longer recognized, so I’ve hooked up an old Mac Cinema Display. This LG monitor is, by the way, the one that Apple recommended when I bought my Mac Mini. Checking online, it seems lots of people are having the same issue on both LGs and BenQs. I wish Apple provided an easy way to back out of an upgrade.
1 Like
I figured out a workaround. Heading into the monitor’s settings, I dumbed down the DisplayPort version from 1.4 to 1.2.
A few Google searches turned up information that this is something that Apple apparently overlooked in all their beta testing. The 1.4 protocol supports data stream compression for 8K monitors. Since my monitor is only 32" 4K, the 1.4 protocol isn’t needed anyway.
3 Likes
Good job Apple
Amazingly, Apple released a bug fix (12.3.1) for this very problem today. 
Such a bummer… I think apple has ruined the display driver functionality in the new macOS Monterey. I have several 27" Viewsonics in my office that only get half the resolution and half the frame rate they are spec’d for on the new M1 MacBooks. Meanwhile all of our older Macbooks on the previous OS work perfectly fine with the monitors. Apple Support has been useless. 