MacBook Pro HDMI not connecting to LG monitor after Tahoe update

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MacBook Pro HDMI not connecting to LG monitor after Tahoe update

Hi guys,

After the Tahoe 26.2 update earlier this week, my Macbook pro 2025 M5 chip has stopped connecting via HDMI to my LG monitor - LG 27MK400H 27" Full HD Monitor

I have tested the monitor with an older macbook 2020 and 2023 and both work just fine, neither of which are running the latest OS.

Here's what I tried so far and nothing has worked:

Restart

Total shutdown

Plug, unplug

Everything Claude and GPT said

Removed the window server file to desktop via terminal

I bought a new 4k hdmi to hdmi and that also didn't work

the macbook connects to a skyworth TV via hdmi

I tried hdmi to USB C which always worked in the past but not anymore

Open to any suggestions, thanks!

MacBook Pro (M5, 2025)

Posted on Aug 28, 2026 1:36 PM

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Answer 1

Aug 28, 2026 1:47 PM in response to chrisdan_99

macOS has become progressively less tolerant of video data packet loss from lower quality cables. In some cases, this means that a setup that worked fine before a macOS update stops working even though nothing about the hardware has changed. If your display is connected via HDMI, make sure the cable is labeled as ULTRA or PREMIUM and is less than 1 m in length. If your display is connected via Thunderbolt/USB-C, make sure the cable is from a reputable brand and capable if high-speed data transfer, and is less than 1 m in length (for Thunderbolt 5 cables, less than 0.5 m in length). Sounds like you've done that, as long as the cable you bought was of high quality and short enough.

See if the problem is present when you boot in safe mode. That process performs some system cleanup and clears caches, and also disables 3rd party extensions that may cause problems.

Start up your Mac in safe mode - Apple Support

If that does not correct the issue, test in a new user account. A newly-created user account will have all settings at default, and if the issue does not occur in that new account then it provides guidance on what may need to be changed to correct the issue.

Add a user or group on Mac - Apple Support

Once the testing is complete, the new account can easily be deleted.

Delete a user or group on Mac – Apple Support

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