MacOS Catalina, 10.15.6. iMac27 late 2012. I have connected two external displays to my iMac and it often works quite well for a long period of time, but then suddenly, after waking from display sleep (not full iMac sleep), my iMac doesn't trigger the external displays any more. Sometimes I can solve it by powering off the iMac and then hoping it will trigger the displays again, but even this is not 100% fool proof. Sometimes I have to do this multiple times.
Things I've tried:
- Only connect one display, doesn't matter.
- Unplugging display cables, wait a few minutes, no result
- Power off iMac, wait a few minutes, power on, works 50/50 of the times
- Detect displays never gives any result.