mac OS Tahoe 26.1 does not connect to LG monitor (40WP95C)

macOS has become progressively less tolerant of video data packet loss due to sub-par cables. There have been several reports of setups that worked in Sequoia not working in Tahoe, with nothing changed but macOS. 

Best recommendation at this point is to try a new cable. Be sure to use high quality cables – HDMI should be labeled Ultra or Premium, USB-C cables should be rated for high-speed data transfer, etc. Also,cables should be as short as possible (≤1 m for most cables, <0.5 m for Thunderbolt 5 cables). That random cable you found in a drawer might or might not work.

In your reply, you mentioned cables (plural). Are you using a dock or hub in between the computer and display? If so, try removing that from the equation and directly connecting the monitor to your Mac with a single appropriate, high-quality cable.

FWIW, I have an LG 5K:2K Thunderbolt 3 display connected via a Stone Pro TB3 dock (via a pair of short TB3 cables) and it works fine with my Mac running 26.1.

The nee cable fixed it for me! I am running dual 40" LG 2K5K monitors and they seemingly stopped being recognized by my M1 Pro MacBook. Once I switched from the LG provided cables to Apple Thunderbolt cables, it worked again immediately.

What I did notice, when using the LG cable, it was trying to connect because I could see the sound icon on that top of my MacBook display attempt to switch to the LG, but the monitor never appeared under Settings - Display.

if it was me then I would try to test the monitor with another computer

and if possible the mac with another monitor to discover if

it's an issue with all monitors connected to the mac

and or if the lg monitor have issues being connected to any computer

you can try to reach out to their official support channels

Get Support (apple.com)

And or

Contact - Official Apple Support

And or

Contact - How to Contact Us - Apple

Or

Genius Bar Reservation and Apple Support Options - Apple

No Apple employees participate here, so no one in the product develop teams, or Apple support will see your post. These are strictly fellow user supported and public communities.

Check or reconnect your cabling with the LG display. I use the LG 32UN880-B 32-inch 4K display with my M4 Mac Mini Pro (26.1) and it is flawless. Recently, I slightly moved the mini and the LG display stayed dark. I then looked at the HDMI 2.1 Belkin cabling and the HDMI cable had been partially pulled out of the mini. Once I fixed that, the display works fine.