The adapter itself seems to be ok.
Hi Chris,
Sorry to hear that your UD-3900 stopped working.
Could you directly contact us at support@plugable.com with the Amazon Order ID so that we could help you to narrow down the issue? Plugable offers 1-year product warranty - if it turned out that the unit got broken, we’ll be happy to send you the replacement.
Thanks!
Sachiko
Plugable Support