Thanks for posting!
A quick note, we don’t officially support beta versions of any operating system. We will of course do our best to help, however we want to set honest expectations up front just in case we are unable to provide a solution.
Based on your description of the behavior, our next step is to get some additional information.
Please keep the dock the connected to your system with the Ethernet cable connected to the dock (even though it is not working) and send the output of our diagnostic utility PlugDebug --> http://plugable.com/support/plugdebug to us directly via email@example.com with ‘For Ticket # 234056’ 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.
* Please do not post the PlugDebug in our public forum *