USB c port not recognizing HDMI adapter and therefore monitor

Hi There,

Hoping you can help me!! I have the wonderful TBT3-UDC3, however I have had a couple of issues of late …

Issue 1 … when I plug in a different laptop, a brand new Lenovo Thinkbook G4 T2 the monitor that is attached to the displayport throws a paddy every 5 seconds, connecting and disconnecting.

Issue 2 … I tried to mitigate this issue by purchasing a USB c to HDMI adapter, but the device does not recognize this. I know the adapter works as when I plug it into the laptop the screen comes up!

Any help would be appreciated!

Best Regards

Hello David,

Thank you for reaching out to Plugable Support!

I am sorry to hear that you are running into issues with your TBT3-UDC3 dock, but I would be happy to help diagnose the issue.

To address issue 1:

First, can you confirm that you are trying to connect to your laptop using the included Thunderbolt 3 cable that came with your dock? We’ve seen issues arise when a third party cable is used.

Next, some steps we’ll want to take are to perform a power-cycle of the unit to reset its internal hub chipset. We’ve seen that this can often restore the dock back to a working state when one or more of its functions are not quite working. To do this, please follow these steps:

  1. Disconnect all USB peripherals and displays connected to the dock
  2. Disconnect the docking station from host machine, then disconnect the power adapter from power
  3. Leave unplugged for 1 minute for power to dissipate
  4. Connect docking station initially into power only
  5. Connect docking station to host machine, then connect USB peripherals and displays, then test for functionality

Please let me know if this helps at all.

To address issue 2:

Our TBT3-UDC3 comes with two “data only” USB-C ports which do not support video output. For this reason, USB-C video adapters will not work when connected to the USB-C ports on the TBT3-UDC3. I am sorry for the confusion.

Please let me know if the power cycle helps or if you have any additional questions!

Thank you,

Plugable Technologies


Thanks for the reply. Let me talk you through the testing I have done …

I have 2 x TBT3-UDC3 docks.

I have a set up where two monitors are Samsung 4k plugged into one of my docks, and on the other dock I have 2 x HP f27.

I also have 2 laptops, Laptop 1 is an HP Dragonfly, Laptop 2 is a Lenovo Thinkbook G4 T2.

On both dock set-ups when I use the dragonfly i experience zero problems with the DisplayPort and HDMI, however the USB c to HDMI connection does not get recognized

On both dock set-ups when I plug in the Lenovo G4 T2 the monitor in the DisplayPort cycles on and off every 5 seconds.

I see your response on the USB C setup … that’s a shame, I was not aware of this when I purchased these products, and is annoying for the price of it!!

Having power cycled both set-ups, I can confirm the issue is still present.

Best Regards

Hello David,

Thank you for your response and for detailing the testing you have done.

I am sorry that the power cycle did not help.

To further diagnose the issues with the Lenovo and the monitor flashing, I’d like to request some logs from your device using our PlugDebug diagnostics tool. With everything still attached to the dock (even if it appears to not be working) please follow the instructions on our PlugDebug page.

It should provide you with a ZIP file containing the PlugDebug logs. If you don’t mind sending it to with the subject titled “Ticket 358014” we’d be able to further assist you from there.

Thank you for your patience through all of this.

Plugable Technologies

Plugable data from the app sent over as requested!

As an update, we were able to identify that the problem was that the dock was connected to a non-Thunderbolt USB-C port on the laptop. Once the dock was connected to the Thunderbolt 4 port on the laptop, the issues were resolved.

Plugable Technologies

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