How do I fix a 2nd display not detected after sleep on a 2012 iMac running Catalina?

running Catalina on a 2012 iMac. 2nd Display erractic. sometimes it works, but after going to sleep it can't see the display. Tried unplugging the display and reconnecting. Nothing. Using top quality HDMI to thunderbolt cable. Just can't detect the display! have restarted Mac numerous time. Nothing. Please help. Driving me nuts!

[Re-Titled by Moderator]

Original Title: 2nd display

iMac 27″, macOS 10.15

Posted on Jun 12, 2025 05:55 AM

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1 reply

den.thed

Level 10

88,810 points

Jun 12, 2025 08:23 AM in response to GonzoGirl

Go to Apple > System Preferences > Energy Saver

set the Computer sleep.. slider to Never

set Display sleep.. to 10 minutes

uncheck the boxes

Then test those settings for a day or two.

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How do I fix a 2nd display not detected after sleep on a 2012 iMac running Catalina?

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