No audio on android after system reset

[samjam]

I use a USB Displaylink adaptor on my Elephone P9000 and my Dell Venue 7840; these worked fine with audio.

I noticed that Wireless Display (Miracast) could not work and reset my devices and Miracast then worked, but now using DisplayLink adaptor I get no audio over the HDMI.

This is with the latest DisplayLink Desktop or the DisplayLink Desktop beta.

(The comment about the Miracast may be a red herring, but it is the reason I reset my devices)

Any ideas?

[samjam]

The Dell Venue is working, for no apparent reason, but the elephone not working. I sent a feedback report via the beta app.