iMac not recognizing monitor with usb-c monitor

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Level 1

4 points

iMac not recognizing monitor with usb-c monitor

I have a monitor with a usb-c port that came with a usb-c to usb-c cable. When I connect the cable to my 2019 iMac and the monitor, the monitor is not recognized. The monitor says no signal detected. The iMac does not show the Arrangement tab under System Preferences -> Displays.

However, if I disconnect the cable from the iMac and connect it to my MacBook Pro or 12" MacBook, they work instantly. The iMac and the MacBook are both running 10.15.5 and the MacBook Pro is running 10.14.6. So I cannot say its because of Catalina. This is my first time trying to connect the iMac to a monitor.

Other attempts to use thunderbolt 3 / usb-c ports on the iMac have been successful: can connect iPad via usb-c and can connect to monitor with HDMI (with usb-c/hdmi adapter). But could there be something wrong with these ports for displaying to a monitor directly through usb-c?

So if the MacBooks work with the monitor with the usb-c cable, why doesn't the iMac?

iMac Line (2012 and Later)

Posted on Jul 10, 2020 9:58 PM

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Answer 1

brenden dv

Community Specialist

Jul 15, 2020 9:06 AM in response to ballgeier

Hello ballgeier,

Welcome to the Apple Support Communities. From your post, it appears there's an issue connecting an USB-C monitor with the iMac. We'll do what we can to help.

Try all the steps here on the affected iMac since we know it's narrowed down to there: Get help with video issues on external displays connected to your Mac

Enjoy your day.

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Answer 2

ballgeier Author

Level 1

4 points

Aug 16, 2020 10:30 AM in response to i_rina

I was not able to get the usb-c to usb-c cable to work, but I was able to get a usb-c to display port cable to work. So I will go with that for now.

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Answer 3

ballgeier Author

Level 1

4 points

Jul 19, 2020 2:22 PM in response to brenden dv

Thanks, I tried what I could from the link provided. Note I am not using any adapters. Just the usb-c cable that was provided with the monitor. I still am unable to connect with this cable connected to the iMac and the monitor.

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Answer 4

i_rina

Community Specialist

Jul 21, 2020 8:59 AM in response to ballgeier

ballgeier,

Got it. The next best thing to do is reset the settings and power delivery on the Mac to ensure there are no conflicts:

To narrow it down, also be sure to check your Mac in safe mode: How to use safe mode on your Mac You can also try a new user as well: How to test an issue in another user account on your Mac

If it only happens in your user and not in safe mode, try removing login items: Open items automatically when you log in on Mac
If it happens in both safe mode and a new user, back up your Mac and reinstall macOS using Recovery: How to reinstall macOS from macOS Recovery

If you're still having issues, reach out to Apple Support directly: Get Support

Take care.

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iMac not recognizing monitor with usb-c monitor

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