Monitor "working" except for black screen

[CatalogK9]

TL;DR: black screen issues might possibly have something to do with power management rather than security issues, maybe?

I'm using the 4URPC 15-in-1 docking station to connect my M1 MBA to a 24" Apple LED Cinema Display via miniDP-to-DP cable. All was (mostly) well until a few days ago, when my screen when to sleep after 15 minutes of inactivity and refused to wake back up.

I had already been on the Sequoia 15.4 RC2 public beta (24E246) and hadn't had any issues up until this point, and despite updating DisplayLink, then using the cleanup tool and reinstalling it, and updating MacOS to 24E248 (no longer beta), and doing all of the troubleshooting suggested for similar issues on these forums and elsewhere, such as deleting/restoring the display preference file, nothing is working.

My laptop assures me everything is working fine, all my peripherals connected through the monitor are working, and I can see what's being shared to that screen in the screen sharing menubar dropdown thing, but the screen remains black, and brightness controls are greyed out or missing. Third-party display management software using software dimming rather than hardware dimming do not have any visible effect. A couple of times during reboots, etc., the screen flickered for the briefest of moments, so it's not like the backlight can't turn on or anything.

One curious thing I've noticed is that System Information shows the usual 500mA current available for the display, but current required is only at 2mA, so perhaps this is less of a security/permissions issue, and something to do with power management instead? I hope this helps y'all find a solution for us soon and with conserably less frustration for y'all.

[mjaroch]

Hello CatalogK9,

Thank you for sharing your problem.

It is possible that this issue is caused by power source.
To make sure, please try to disconnect the device from its power source and connect it back again. Reconnect your MacBook and display and check if the issue persists. You can also try alternative connection method to rule out cable-related issues.

If you have already used the End-User Cleaner Tool, I assume you have installed the latest version of the DisplayLink driver.

If your problem still occurs, please collect data by following this steps.

[CatalogK9]

I did all of these steps already, and sent an email with the diagnostic file a few days ago (Monday, I think).

[mjaroch]

Hello CatalogK9,

Please wait for a response from our engineering team.
Hope it will help you solve this issue!

[CatalogK9]

I've replied to the email with some screenshots, thank you