Got my Plugable ud-3900 today. Install drivers and plugged everything in. Mouse/Keyboard work and other USB devices. Plugged in HDMI cable and nothing. Very frustrating… Please help.
Found a post that resolved my problem. Needed to download and uninstall of plugable software and install of the new version and the HDMI starting working! 
Thanks for posting and great to hear that reinstalling the DisplayLink drivers helped!
If you happen to run into any other issues we’d be happy to help!
Thank you,
David W.
Plugable Technologies
www.plugable.com/support
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