UD3900 docking station no longer recognizing monitor

For a long time I was using the UD3900 docking station with my MacBook Air (2014) to have a 2nd external monitor. Monitor #1 went from my thunderbolt directly to my one TV monitor. Monitor #2 went from my USB 3.0 to the Docking station, from the DVI to the 2nd TV monitor(HDMI). The set up, while a little cumbersome with wires, worked very well. Now, the 2nd monitor is not receiving the signal from the docking station. I have tried using the HDMI output from the docking station with no success. My Mac iOS updated and current and just updated the docking station’s firmware and still no success. I realize my MacBook is older but it still works great. I would prefer to not buy a new one and just update it’s SSD memory when I have to. So…

  1. Can the docking station be “fixed” so I can get back to having a second monitor?

  2. Do I have to buy a new docking station?

  3. Am I SOL and need to get a new MacBook with a Thunberbolt 3 and appropriate docking station?

Hi Ken,

Thank you for posting! I am sorry things are not working as expected while using your Plugable UD-3900 docking station with your MacBook Air and I would be happy to help.

I cannot be sure of the cause of the problem based on the description alone, so I am afraid that I cannot answer your questions at this time.

That said, based on your description of the behavior one quick thing to double-check is that the source video input setting within the TV monitor that is not working is set to the correct video input. This is important because TVs with multiple video inputs may not always switch to the preferred one automatically.

If double-checking the source video input setting did not help, then our next step is to get some additional information.

Can you please reach out to us directly via support@plugable.com referencing Ticket #- 337683 with the following information?

  1. The Amazon Order ID number for your Plugable UD-3900 purchase

  2. While the dock is connected to your laptop and the TV monitor is connected to the dock (even if not working as expected) the output of our diagnostic utility PlugDebug → https://plugable.com/pages/plugdebug

That information will allow us to match things up and will help us determine the next steps.

** Please do not post the Order ID number or the PlugDebug file here in our public forum. Please only include that information within your direct email **

Apologies again for the frustration, and thank you for giving us the chance to help!

Plugable Technologies

Thank you for your response. Fortunately it has become a moot point (not to mention I don’t have the Amazon order ID number any more. I’ve had it for a long time). After I posted this message, I continued to comb through this forum for a possible solution and I found it. While I did update the firmware for the docking station itself, I found another thread that indicated the Display Link Manager also needed to be updated. After doing so, my problem was fixed.

Thank you again for replying so quickly.


Hi Ken,

Thank you for getting back to us with the update, and you are of course most welcome for the help.

I am glad to hear that everything is now working as expected after having updated the DisplayLink driver, and I thank you for sharing the details of the solution in this specific case that is much appreciated.

Please let us know if you need any help in the future, and please have a good day!


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