TBT3-UDV, MBP 2017, 2 HDMI monitors

I have a brand new 15" MBP 2017, new Plugable TBT3-UDV dock, and two 23" ASUS 1080p monitors with HDMI support.

Monitor #1 is connected via DisplayPort-to-HDMI adapter.
Monitor #2 is connected via Plugable USB-C to HDMI cable.

My problem is that only one monitor works at a time. The first monitor I connect (either #1 or #2) works just fine while the second monitor acts like it is not receiving a signal. In other words, if I connect Monitor #1 first then Monitor #2 does not work. If I connect Monitor #2 first then Monitor #1 does not work.

Currently I am working around the problem by connecting Monitor #2 directly to my MacBook. However this defeats the purpose of the dual-monitor dock.

Please help!


Hi Greg,

Thank you for contacting us! I am sorry your new docking station is not working as expected and I would be happy to help.

Thank you as well for the excellent detail you provided that is much appreciated. A quick question for you…

Can you confirm that you are using only the 0.5 meter Thunderbolt 3 cable we included in the box with the dock to connect it to your system? I ask because other cables can cause similar problems. If not already, please switch to using the included cable to see if that helps.

If switching to the included cable did not help (or if you were using it already) our next step is to get some additional information. If you would, please keep the dock connected to your system with both monitors connected to the dock (even though one is not working) and send the output of our diagnostic utility PlugDebug –> http://plugable.com/support/plugdebug to us directly via support@plugable.com with ‘For Ticket #230505’ in the subject line. This will allow us to match things up and examine some log files from your system to help determine the next steps.

Thank you in advance for your patience, and giving us the chance to help!

Plugable Technologies

Yes, I am currently using the 0.5 meter Thunderbolt 3 cable to connect from the dock to my MBP.

At first I was disappointed in the short length but then I realized the shorter TB cables support 40 Gbps transfer speeds whereas longer TB cables only support 20 Gbps.

I appreciate your help! I will try out the diagnostic utility you mentioned and will post again after I have emailed the info.

Done - The zip file has been emailed to support@plugable.com

Thanks Greg! I just sent my direct reply, please let me know if you do not receive it.


Fantastic support process! The final steps were completed via email. Fast, decisive service.

Just wanted to post here in case anyone else ran across my support thread. Plugable gets an A+ in my book.