I have the UD-3900PDZ on a MacBook Air M1 and it will not recognize my second monitor through HDMI port

Is there and update or driver that need to be updated


Thank you for contacting us, I am sorry this is not working as expected and I am happy to help!

The UD-3900PDZ USB-C Triple HDMI Docking Station relies on two Graphics Technologies to support up to three external displays.

The HDMI 1 “Alt Mode” output port relies on the host computer’s USB-C DisplayPort Alternate Mode functionality, this is an optional USB-C feature. The Apple MacBook Air with M1 processor can support a single external display using USB-C DisplayPort Alternate Mode. This also requires connecting the docking station directly to a USB-C port on the host computer with the original USB-C cable provided with the docking station, Apple’s white USB-C charging cable does not support USB-C DisplayPort Alternate Mode video data.

The HDMI 2 and HDMI 3 “DisplayLink” output ports rely on the DisplayLink Manager App to enable and control these displays. We provide step-by-step installation and configuration instructions for the DisplayLink Manager App here ( https://kb.plugable.com/1185378 ).

Please let me know if the above helps to get the external display detected and working, and if it is still not working please let me know the manufacturer name and model of the external display, and which port it is connected to on the docking station.

Thank you,

Plugable Technology

I am having a similar issue. I have a Macbook Pro 13" with the M1 chip running Monterey OS and have connected two hp monitors (a hp 24mh and a hp vh240a) to the HDMI ports in a usb 3.0 Dual Monitor Horizontal Docking station (plugable.com/products/ud-6950h). However I can only get one or the other external monitor to work. I have downloaded and installed the Display Link driver (1.6.1) and according to the ‘displays’ section under system preferences the computer can detect both external displays. One just remains black. Any help would be greatly appreciated.

Hi dsharrock,

Thank you for contacting Plugable, most likely the issue you are seeing is unrelated to this post due to the hardware difference between the UD-3900PDZ USB-C Triple Display Docking Station and the UD-6950H USB 3.0 Dual Display Docking Station.

I recommend starting by connecting the two external displays to the docking station, one to each “Display #” port pair ( for example connect the HP 24MH to “(1)HDMI” and connect the HP VG240A to “(2)HDMI” or “(2)DP++” on the back of the docking station ). If they are both connected to the same “Display #” port pair than only one will be active at a time.

Next I recommend we gather some additional information from your system.

If you would, please keep the dock connected to the computer with monitor(s) connected to the docking station (even though one may not be working) and attach the output of our diagnostic utility PlugDebug ( http://plugable.com/support/plugdebug ) to an email to ‘support@plugable.com’ with the subject line ‘UD-6950H Only Single Display Working macOS 12’ as this will allow us to examine some log files from your system to help determine the next steps.


Plugable Technology

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