Big Sur dual monitors. Only one displays

Question

Created Aug ’20

Replies 6

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Views 2.3k

Participants 6

I have two monitors. When i log in only one displays and the other is a black screen, though it is still on (getting signal)

Every now and then I log in and the other will work instead

Is this a known bug? I have tried multiple resolutions and refresh rates to no avail.

Macpro6,1

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Answer 1

lsackette OP

Dec ’20

Any update on this? I am seeing a similar issue. I have an external monitor, which works fine until the computer goes to sleep. When I login after the display goes to sleep, I only get my laptop display. I have to unplug or go to the Display setting page to trigger the external monitor to come on.

If I move my mouse to the edge, my mouse moves off the laptop screen as it if is on the external display.

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Answer 2

DMC52 OP

Dec ’20

I have run Catalina for several years with two external monitors that I "located" using the Displays tab in System Preferences and then choosing "Arrangement."
I just downloaded (upgraded?) to Big Sur and the "Arrangement" tab no longer appears.

Anyone help?

1

Answer 3

DMC52 OP

Dec ’20

It has often been the case that the external displays go to sleep and the cursor moves off the laptop screen as if going on the external monitor but the screen is black and no cursor appears. I have always resolved that by turning the external display off and back on.

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Answer 4

TBA4 OP

Feb ’21

Any update or fix? Same issue here - two dell 2419HX connected via CalDigit TS3 plus - one via DP the other via USB-C to DP cables. Only one monitor works at a time. Apple display only recognizes one monitor at a time. Any help appreciated! thanks

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Answer 5

chelms OP

Jun ’21

See my answer at https://developer.apple.com/forums/thread/666645?page=1#679566022 .

Basically, plug in both monitors (or dock with 2 monitors) only on the LEFT side of the laptop.

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Answer 6

rosiecastle OP

Dec ’21

Hello, I have the same exact issue. Getting signal from my external display, but when I switch off the mirroring option then I get a black screen. I contacted apple and they told me to downgrade to Catalina. However, I have read users struggling with that as well. Did you solve this problem?

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