Ud-3900pdz no hdmi output on alt-mode port

The display link ports work fine but the alt mode port shows no signal. Ive tried resetting per support suggestions but to no avail.

I am on an m2 MacBook air if that helps.


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

I recommend starting by double-checking to ensure the docking station is connected directly to the MacBook with the original USB-C data cable provided with the docking station. USB-C cables sold online as “charging” cables, and the Apple USB-C “charging” cable do not support USB-C DisplayPort Alternate Mode video and will prevent the “Display 1” output port from working.

Connecting the docking station through a USB hub, USB-C cable extension, or USB-C to USB-A adapter will also prevent the “Display 1” output from functioning.

Please let me know if this helps to get all three external displays working, if not we can go from here.

Thank you,

Plugable Technology


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.


Plugable Technologies