I have two monitors - a ThinkVision, another Apple 27" cinema. I have in the past individually connected them to 2018 MBP Retina via Thunderbolt. OS is Catalina. 32GB RAM. Radeon Pro 560X 4GB.
When I tried to connect these 2 displays at once, following happened
- the dock vanished, no way to bring back
- wallpaper on all displays (including Mac's native) blacked out. I can see desktop icons though
- 4 finger gestures don't work
I have tried the following:
- connect only Apple display
- connect Apple display directly on USB-C via Thunderbolt to USB-C adapter
- slide mouse on the edge of the display to attempt to bring dock there
- reset NVRAM, PRAM and delete the .plist files as explained here
Previously, each of them have worked nicely individually. After this attempt, even individually connecting Apple display gives me the same problem (can't go back to previous state). However, the ThinkVision display works fine individually with none of these issues.
Does it have to do with refresh rate, or Resolution supported by Mac, etc.?