HDMI Alt Port not connecting my third display

I have a Macbook Air M1 chip with OS Sonoma. I’ using the UD-3900PDZ triple HDMI Display Hub. I have display link installed and it recognized two of my monitors, but my third monitor which is connected to the alt port is not showing up. Please assist!!

Hi,

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

I recommend we start by ensuring the docking station is connected directly to the computer using the original USB Type-C data cable provided with the docking station. USB Type-C “charging” cables like the white cable provided with the MacBook do not support USB Type-C DisplayPort Alternate Mode video and are not capable of enabling the “HDMI 1” output on this docking station.

I also recommend we set all detected displays to extended desktop mode in the Display Settings menu:

  1. Open the Apple Menu > System Settings
  2. From the left column select “Displays”
  3. On the right pane, for each of the displays at the top ( you may have to scroll to the right )
    3.1) Select the external display from the top of the window
    3.2) From the “Use as” drop down menu select “Extended Display”
  4. After setting all external displays to the “Extended Display” mode, check for all displays to show the desktop background
    4.1) If the displays are still not detected correctly please unplug the docking station from the computer and restart macOS
    4.2) After logging back into the computer reconnect the docking station and check for the displays to be detected
  5. Arrange the displays using the “Arrange…” button at the top of the “Display Settings” panel

Please let me know if this helps to get all external displays detected and working within macOS, and if not we can proceed from here.

Thank you,

Pat
Plugable Technology
support@plugable.com

Hello,

We’re closing this thread due to inactivity, but if you have any further questions please feel free to contact support@plugable.com and we’ll be happy to help.

Thanks,

Pat
Plugable Technologies
support@plugable.com