I’m using a MacBook Pro 14″ M1 Pro and I have 2 external Dell U2520D connected via USB-C. I also power my MacBook Pro from the same USB-C. Every once in a while when I plug in my MacBook I end up with three black screens.
When I connect my MacBook with the two USB-C cables from the monitors and open the lid, the external monitors show my desktop and my MacBook also shows a desktop. It notices my Apple Watch and automatically unlocks my MacBook. Then after a second or two, all the screens go black and stay black. Space bar, Esc, mouse movement, nothing turns on the screens. As if the brightness is 0.
Disconnecting both screens doesn’t turn on my MacBook screen, it stays black but unlocked and while I can’t see anything, it’s just like I’m using it. I can open applications etc., I know this because of some sounds.
When I connect one external monitor, it turns on and shows my desktop on that monitor. Connecting a second monitor does the same. So I end up with two working displays, but my MacBook screen remains black.
When I go into the monitor settings, I see all three monitors. I can change the brightness of the built-in MacBook display, but it makes no difference. I can’t get it to light up again.
I have also noticed that the external displays are not scaling correctly. The hover effects of my mouse are on a different part of the screen than where my mouse actually is. However, the click events are fired from where the mouse is on the screen.
Rebooting fixes the problem and I can disconnect and reconnect several times before the problem occurs again.
Does anyone know what could be causing this?