2 Monitors Detected, but only 1 displaying picture
 

I'm on a 2020 MacBook Air. I've got 2 monitors connected via my Plugable dock via HDMI and I can see both monitors are detected when I'm in display preferences and DisplayLink preferences. Both monitors also have a blue light, indicating they're connected.

However, monitor 2 will only display a picture when it is set to mirror monitor 1. Both monitors are the same model (acer XF251Q).

In the screen layout in display settings, monitor 2 is represented as much smaller than monitor 1, but I have not yet found anything I can change to fix that and make the monitor image visible.

Even if I unplug monitor 1, monitor 2 still just a black screen while being detected. Problem persists even if I swap the HDMI ports.

Mirroring monitor 1 on to monitor 2 is currently the only way to get picture.

Based solely on your description, I would suggest replacing the HDMI video cable being used with the affected display in order to rule out the HDMI video cable as a contributor.

I tried multiple cables. Same cables work successfully in mirror mode and on a separate make/model monitor I brought in to try. I feel like this has something to do with the 2 monitors being the same model.

I have now purchased a displayport to hdmi cable and the same problem is still happening.

When it’s not mirroring another monitor, Graphics/Displays in Software Info list it as 768x1024.

When it is mirror the MacBook and displays an image, Graphics/Displays in system info list it as 2880x1800 with a UI that looks like 1440x900.

I've confirmed this is an issue with newer versions of DisplayLink and M1 Macbooks.

Two options:
- Downgrade to DisplayLink 1.5
- Switch your monitor to a 30hz refresh rate

Does anyone have any more options if none of the above works for the same problem?
I can't change the refresh rate of my monitors, and none of the legacy releases works either

( tried all of the alternatives back to 1.4 which isn't officially supported by OS Monterey.)

I have exaclty the same issue on my M1 with Monterey:

macOS Monterey version 12.3.1
MacBook Pro M1, 2020
Display Link 1.6.1

Both screens detected but only one showing something. Other screen is turned on and auto detected on HDMI port but nothing showing.

One screen is a 1440p 144hz other is 1080p 144hz. The 1080p is not working. When i mirror display from main to the 1080p monitor all monitors work but that is useless.

Tried other ports on monitor, different cables, different resolutions but nothing works. Other setup with two of the same monitors (different from what iam using now) does work without any problems. Maybe the issue is two external monitors with different resolutions?

Working for now... (hope this doesn't jinx it)
 

MacBook Air M1 2020
Monterey 12.3.1
DisplayLink Manager 1.6.1 Build 59.135

Targus DOCK120AP with own power supply
MBA M1 plugged in using 30W adaptor

Old set up was
Dell P2319H (1) using HDMI to HDMI
Dell P2319H (2) using DVI to HDMI

I've managed to get dual set up working again by changing monitor 2 to DP to DP cabling

Switching the cabling above for some reason caused unstable signal on monitor 1 (DP DP)

Things tried (no order)
- Downgrade to Big Sur
- DisplayLink old installs (1.5, 1.6 versions etc.)
- Delete HD and clean install of OS (realise not an option for all)
- Power cable pull tricks etc
- NVRAM / SMC resets
- Validated monitor working, cabling working etc.
- Deleting com.apple.windowserver.plist

Odd things found
- When stopped working initially, issue was monitor 2 not receiving HDMI signal
- Inverting cabling so monitor 2 was HDMI to HDMI didn't help
- A 'simple' single HDMI external monitor via USB-C hub didn't work but did work on a smart TV
- After clean OS install the issue appeared to be active monitor (could move mouse onto it / lose windows over there) but screen all black (monitor did not report no signal)

I've made Apple well aware of the issue and the discussions online (to extent that helps anything right now)

The inconsistency (it stopped working after it went to sleep but now it works again) of course points to OS...

But did you have the same problem as OP? Our issue is that both screens get detected but nothing showing on one of them. And this workaround is just waaaay to much work :p

I've got two identical Dell U2515H, where the second one doesn't work unless being mirrored to. So I have the same resolution for both, and the same issue.

I did however luckily solved the issue for me. I swapped places of my HDMI cables, and then it worked. I guess on of the cables are of an older version and wasn't compatible with the displaylink adapter.