Same problem... finally got sick of restarting the machine, simply to restore the display on the 2nd monitor.
I have:
- 2009 cMP w/ latest Monterey Beta
- Radeon RX 580
- 2 Samsung 32" UHD monitors (both plugged in via HDMI for consistency, although I did try swapping 1 of them to DP during this process)
I picked up the monitors when they went on sale at CostCo (around $250ea) about a year ago. I was replacing to old ViewSonic 27" screens. Never had the problem on the ViewSonic's on any MacOS version(s), but am randomly experiencing this since adding the 4k screens.
I stumbled upon 'preview page content' when using Google, that mentioned "don't use DP v1.2. use v1.1." I clicked on the post to read more, but (oddly) couldn't easily find that content. figured I'd give it a go, but didn't see any difference.
did some more searching and ended up on this thread. as I was reading through, I was thinking "hmmm... no go on DP version change, but HDMI change?" so, I changed HDMI mode from v2.0 to v1.4 and BAM. screen popped back on, just after clicking on the 1.4.
I set the DP version back to v1.2, just to see if it happens again... and if it doesn't, I'll assume that it'd requires both:
- DP v1.1
&
- HDMI Mode v1.4
There's always the chance that those versions have nothing to do with what happened... but, we'll see. if nothing more, hopefully this will at least prevent me from having to reset to recover the second screen. and, if this is the SOLUTION, I'll report back in a few weeks to update my post w/ SOLVED.
So, here's the big funny... both screens were set to DPv1.2 & HDMIv2. only 1 of them (same one) wouldn't wake from sleep throughout this entire time. seems kinda odd, no?
hoping this helps out the next guy/gal!