Mac Pro 16" left side HDMI out not working - screen flashes and does not connect. Right side works fine. Multiple adapters tested including apple offical

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Mac Pro 16" left side HDMI out not working - screen flashes and does not connect. Right side works fine. Multiple adapters tested including apple offical

Today I bought an official usb-c to HDMI adapter as I thought this could be the issue... but its not.

As the title says, when connecting to the 2 right USB-C's the external monitor connects fine.

When connecting to either of the left 2, the laptop screen flashes on and off as does the touch bar icons. It does this flashing indefinitely and does not connect to the external display.

Could it be a hardware issue?

MacBook Pro 16", macOS 10.15

Posted on Jan 5, 2020 1:06 PM

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Answer 1

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booni3 Author

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Jan 5, 2020 1:11 PM in response to booni3

Update: I though as I was writing that to try a reboot and try and rule out hardware.

If I reboot the computer with the USB-C connected to either of the left 2 ports BEFORE the computer starts booting then the screen connects.
If I reboot the computer and then plug the USB-C in afterwards, I get the same flashing issue on the laptop and nothing happens on my external monitor.

I am using an LG Ultra Wide monitor if that makes any difference, but as I say it all works fine when using either of the 2 right ports so I think this point is irrelevant.

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Answer 2

Jan 5, 2020 1:36 PM in response to booni3

Try the SMC and NVRAM reset, then ring up Apple Support.

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Mac Pro 16" left side HDMI out not working - screen flashes and does not connect. Right side works fine. Multiple adapters tested including apple offical

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