External monitor displays "Input not supported" when MacBook Pro lid is closed

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External monitor displays "Input not supported" when MacBook Pro lid is closed

Hello,

I have a 16" MacBook Pro and I am trying to display to an external monitor while the laptop is docked and closed. This function has been working since I bought the laptop, but has recently not worked. I have the laptop on AC power and hooked up via HMDI with a USB-C hub. I also have a wireless keyboard and mouse connected with Bluetooth. The monitor displays fine when the laptop is open, but as soon as I close it, the display turns black and displays "Input not supported." Curiously, the speakers still output sound even though they are hooked into line-out on the monitor itself.

So far I have tried messing with the resolution and color profiles, which haven't seemed to solve the problem. I also tried to clear the NVRAM.

Any help would be appreciated.

MacBook Pro 16", macOS 10.15

Posted on Feb 2, 2020 8:22 PM

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Answer 1

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BobTheFisherman

Level 9

79,675 points

Feb 3, 2020 7:14 AM in response to stoutmiser

Confirm that you are following the instructions located here: Use your Mac notebook computer in closed-display mode with an external display - Apple Support

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Answer 2

stoutmiser Author

Level 1

9 points

Feb 3, 2020 9:24 AM in response to BobTheFisherman

That's correct. I've followed those instructions. Also both methods of getting into closed-display mode, that is closing the laptop after the display shows on the external monitor, and having the laptop in sleep mode and waking it with the monitor connected did not work. Both times it displays input not supported.

Just to confirm, the monitor does work when the MacBook is open and connected. I have it connected to AC power, and it is connected to the monitor through a USB-C hub with HDMI.

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External monitor displays "Input not supported" when MacBook Pro lid is closed

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