USB Ports On Back Not Working Properly With MacBook Pro

I have a MacBook Pro connected to the UD-3900PDZ via a USB-C cable. I have an USB Hub (that is powered) connected to the dock. If it is connected to a USB port in the back of the dock, none of the devices work. If I plug it into the front of the dock, everything is operational. If I switch out my Mac with a Windows 10 machine that is connected via USB-C, I don’t experience the same problem. The Hub connected to the back of the dock works and all of the connected devices work.

Any help getting the Hub connected to the back of the dock and all devices plugged into the hub operational while connected to my Mac would be appreciated.


Hi Art,

Thanks for contacting us! I am sorry this is not working as expected.

Based on your description of this behaivor our first step is to get some additional information from the Apple system in the working and non-working configurations to see exactly how the computer is ( or is not ) detecting the connected USB hub.

If you would, please keep the dock connected to the front port of the Apple computer, where the hub is working and connected USB devices are detected, then run and attach the output of our diagnostic utility PlugDebug ( ) to an email to ‘’ with the subject line ‘Ticket #381434 - Attention Pat’ as this will allow us to examine some log files from your system to help determine the next steps. I recommend appending “-hub_front” to the end of the zip file ( before the .zip ) extension to clarify this file is in the working position.

Next, please connect the USB hub to the back of the docking station and verify the devices are not detected, then re-run the PlugDebug utility as above, please append “-hub_back” to the file name and attach to the reply email to our support team.

I will examine and compare the working and non-working log files and see if this provides any information that may help to work around or duplicate this issue on our test computers.

Thank you,

Plugable Technology

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