Why does my MacBook Pro M4 fail to recognize two displays simultaneously?

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Why does my MacBook Pro M4 fail to recognize two displays simultaneously?

I have 14" Macbook Pro with M4 Pro and trying to connect two displays: Asus ROG PG27UCDM and MSI MPG 274URF QD. Both displays have usb-c port and usb-c to ubs-c cable in their package.

When I connect them one by one, both work well in 4k and support their max frequency (up to 240 Hz in case of Asus).

When I try to connect both of them at the same time - only one display is recognized - one that was connected first.

I tried to connect one of them with HDMI with same result in most cases, but sometimes macbook actually recognize second display and able to show image on both with max frequency 120Hz.

What could be the issue? How to make display recognition more reliable? Is it software issues with mac os or hardware issue of my specific laptop?

[Re-Titled by Moderator]

MacBook Pro 14″, macOS 15.4

Posted on May 14, 2025 1:02 PM

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Answer 1

May 14, 2025 9:23 PM in response to mvvChief

You say that one of your displays supports a refresh rate of 240 Hz. Your MacBook Pro can drive a display at 240 Hz over HDMI, but only at the cost of limiting you to a single external display.

MacBook Pro (14-inch, M4 Pro or M4 Max, 2024) - Tech Specs - Apple Support

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M4 Pro

Simultaneously supports full native resolution on the built-in display at 1 billion colors and:

Up to two external displays with up to 6K resolution at 60Hz over Thunderbolt, or one external display with up to 6K resolution at 60Hz over Thunderbolt and one external display with up to 4K resolution at 144Hz over HDMI
One external display supported at 8K resolution at 60Hz or one external display at 4K resolution at 240Hz over HDMI

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Use an external display with your MacBook Pro - Apple Support also makes no mention of support for refresh rates greater than 144 Hz, except in the case where you have a single external display, with a resolution of up to 4K, that is connected to the HDMI port. Then the refresh rate can be up to 240 Hz.

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Answer 2

May 15, 2025 11:01 AM in response to mvvChief

The Mac does not rely on Windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

so try doing some of those things and see if the display comes alive.

Your Mac re-acquires each and every display anew when you start up. This allows you to re-arrange displays and Restart to move them around.

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Answer 3

mvvChief Author

Level 1

5 points

May 21, 2025 1:16 AM in response to Grant Bennet-Alder

Tried Detect displays button, and it has no effect. The most effective way to make macbook detect both displays is to connect them at the same time. It still don't guarantee that both will be detected but it eventually happen and it seems to be faster than reconnecting displays one by one

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Answer 4

mvvChief Author

Level 1

5 points

May 15, 2025 1:04 AM in response to Servant of Cats

I don’t think the issue is related to refresh rates — I only mentioned them to point out that both displays work fine individually.

As I said, on rare occasions the system does recognize both displays when using the USB-C + HDMI configuration, and it sets both to 60 Hz by default. I can then change them to 120 Hz, and they continue to work. So it doesn’t seem like the high refresh rate is preventing the displays from connecting.

And although system should remember the displays and their configurations. Even if I manually set both to 60 Hz, it doesn’t help — the next time I reconnect them, they’re still not always recognized.

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Why does my MacBook Pro M4 fail to recognize two displays simultaneously?

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