2nd monitor mirrors, cannot be detected

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Level 1

12 points

2nd monitor mirrors, cannot be detected

Hello!

I've been using an external monitor for 8 months now and have decided to add a 2nd external monitor. My dock has room for 2 HDMI, so I've plugged the 2nd monitor in, but I can only mirror the other monitor. When in system preferences > display, I cannot get it to detect the second monitor, even though it is successfully mirroring the 1st.

I've tried changing the resolution to scaled, restarting, sleeping, etc. No luck.

Any advice?

MacBook Pro 16 inch, 2019

macOS Monterey

MacBook Pro 16″, macOS 12.3

Posted on May 22, 2022 2:45 PM

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Answer 1

sarahfeaster Author

Level 1

12 points

May 22, 2022 3:18 PM in response to Grant Bennet-Alder

Hello there - thank you for your quick response!

I'm using this dock:

USB C Docking Station Dual Monitor,USB C Dual Monitor 2 HDMI Adapter,Triple Display 4K HDMI&VGA,14 in 1-3USB3.0&2USB2.0,Gigabit Ethernet,100W PD,SD/TF Card Reader,Type-C Data Transfer,3.5mm Audio

https://smile.amazon.com/gp/product/B08HM1LF9P/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The monitor is connected to the dock via HDMI.

If I unplug the 1st monitor, the 2nd monitor works fine and it shows up under a different name in my Display dialogue box. As soon as I plug the 1st monitor back in, all the screens refresh and then the 2nd monitor name disappears from the display settings.

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Answer 2

May 22, 2022 4:44 PM in response to sarahfeaster

That one can support two independent displays, each different from the built-in if desired, at up to 4K each.

That ad goes out of its way to point out the ThunderBolt symbol on the input cord, and says it will NOT work with 'only' USB-C

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Answer 3

May 22, 2022 2:59 PM in response to sarahfeaster

what Make&Model dock, exactly?

what connection method your Mac? genuine ThunderBolt, with the Thunderbolt symbol on the cable, or "regular" USB-C ?

If you disconnect the first display, does the second display operate as expected?

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Answer 4

May 22, 2022 3:39 PM in response to sarahfeaster

Thanks for that link. If you look at the pictures in the left column, one of them shows Mac displays. The top illustration there there display "mirrored". in this case, the built-in display and all three external displays show the same picture.

Now look closely at the second picture.

The MacBook shown has one picture, and each of the other displays has a different picture, but IDENTICAL to each other.

The Mac does not support multiple displays on one USB-C cable. It does support up to two displays on a genuine ThunderBolt cable, When connected to a genuine ThunderBolt device (Dock or Display) as the first device.

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Answer 5

sarahfeaster Author

Level 1

12 points

May 22, 2022 3:53 PM in response to Grant Bennet-Alder

Thank you for your help! So if I used something like this, instead, I could use the two external monitors as two separate screens instead of 1 image mirrored on both?

https://smile.amazon.com/WAVLINK-Thunderbolt-Converter-Supports-4096x2160/dp/B08D8WLR79/ref=sr_1_23_sspa?crid=4RIE4Z8ONR9O&keywords=thunderbolt%2Bto%2Bhdmi&qid=1653259866&sprefix=thunderbolt%2Bto%2Bhdmi%2Caps%2C105&sr=8-23-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyQVo4UTRDNEEzR1dZJmVuY3J5cHRlZElkPUEwMTQzODA4MlpFVVpERkNLNE84SSZlbmNyeXB0ZWRBZElkPUEwMTU5MjAxV0xEMUhQQTRaNFBQJndpZGdldE5hbWU9c3BfbXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ&th=1

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Answer 6

sarahfeaster Author

Level 1

12 points

May 24, 2022 6:20 PM in response to Grant Bennet-Alder

Thank you, again, for all your help! My new ThunderBolt display dual monitor dock arrived today and works perfectly. You're a lifesaver!

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2nd monitor mirrors, cannot be detected

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