External display won't connect at full resolution

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Level 1

4 points

External display won't connect at full resolution

I have a 2018 Macbook Pro with touchpad and until yesterday I have always been able to connect to my external display at 1440p but now, no matter what I try, I can only connect at a max of 1080p which is unacceptable for my photo editing and graphics work. In the Displays panel of System Preferences, the default setting is 1080p and when I click "Scaled" all of the options are 1080p or less, even when I option-click.

For reference, the external display is an Acer KG271U and I've always connected via HDMI through the official Apple USB-C Digital AV Multiport Adapter to a Thunderbolt 3 port on my MBP. I've also connected the display to a Windows PC which is successful in connecting a the full 1440p resolution of the monitor.

I've tried the following to get it to work on the Mac:

restarting my MBP
disconnecting and reconnecting the HDMI on both ends
using a different HDMI cable
power cycling the display
connecting the adapter to all four of the different Thunderbolt 3 ports on my Mac
and nothing works.

Any help or suggestions would be greatly appreciated.

MacBook Pro 13″, macOS 11.4

Posted on Sep 5, 2021 5:33 AM

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Answer 1

Sharhari

Level 5

6,293 points

Sep 6, 2021 10:56 PM in response to brandondeth

Hope you are using appropriate cable, About HDMI cables there are:

Standard HDMI cable (720p and 1080p, HDMI versions 1.0 to 1.2a.)
High Speed HDMI Cable (1080p and 4K, HDMI versions 1.3 to 1.4a.)
Premium High-Speed HDMI Cable (4K/UltraHD resolution video 60Hz HDR, HDMI versions 2.0/a/b.)
Ultra High-Speed HDMI Cable (8K video with HDR and even 10k resolution, HDMI version 2.1.)

Since your monitor supports DisplayPort: Test with Thunderbolt 3 (USB-C) to DisplayPort cable and see if it helps.

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Answer 2

karina184

Community Specialist

Sep 6, 2021 6:30 AM in response to brandondeth

Hello brandondeth! Thank you for participating in the Apple Support Communities.

We understand that your Mac isn't connecting to your external display at 1440p, as it was previously able to. We'd like to look into this with you to see how we can help.

You've taken some great steps up to this point to try to resolve this issue. If you connect to another display that supports 1440p, are you able to use that resolution? Or does it only allow you to connect at 1080p or less?

If you're able to connect at 1440p with another display, contact the manufacturer of the first display to look into this issue further. If you're still unable to connect at 1440p with the second display, try resetting the following to see if they help:

Reset NVRAM or PRAM on your Mac - Apple Support

How to reset the System Management Controller (SMC) on your Mac - Apple Support

Make it a great day!

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Answer 3

brandondeth Author

Level 1

4 points

Sep 7, 2021 6:14 AM in response to karina184

Thanks, Karina. The only other display I have available is a 4K tv which I was also unable to connect at anything above 1080p. I will try resetting the NVRAM next and see what happens. Thanks for your suggestions.

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Answer 4

brandondeth Author

Level 1

4 points

Sep 7, 2021 6:18 AM in response to Sharhari

Thanks, Sharhari. I was previously able to connect to the monitor at 1440p with the same high speed HDMI cable that I'm using now. I've also tried switching to a different high speed HDMI cable and also connecting to a 4K TV using a premium high speed cable and none of which allow me to connect at any resolution higher than 1080p. Unfortunately I don't have a DisplayPort to Thunderbolt adapter so I am unable to test that solution right now.

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Answer 5

brandondeth Author

Level 1

4 points

Sep 7, 2021 5:55 PM in response to karina184

Ok I've now tried resetting the PRAM and resetting the SMC. I've also tried connecting to my 4K TV using premium high speed HDMI (which previously worked at up to 4K resolution) but now I can only get up to 1080p on external displays. Is there anything else I can try? If not, what course of action can I take to restore functionality to my MBP?

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Answer 6

Sep 7, 2021 6:49 PM in response to brandondeth

Later versions of MacOS appear to tabulate errors that occur in transferring data to the display. so if your cabling is good, but not great, you can see the resolution drop back to what runs without error.

A suggestion was made that you connect with a DisplayPort cable/adapter.

Also, have you read this article? which model of the Apple adapter do you have?

About the Apple USB-C Digital AV Multiport Adapter - Apple Support

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External display won't connect at full resolution

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