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* Mic testing in what apps? Does the issue happen in all apps?
* Have you tried closing the webcam shutter which might "release" the webcam and mic from the apps, wait 10 seconds, then opening the webcam shutter?

@DELL-Chris M​ Thanks again, Chris.  All of those settings were set as you suggest, apart from fast wake up - I've changed that, I'll let you know if it has an effect - thanks a lot.

Are you saying  fast wake up has made it worse? 

Zoom seams to like to default to Muted. (I assume the red light wasn't on, at the bottom left corner) 

@Andy K​ Hey - no, I don't think that fast wake up has made any difference in particular.  There's nothing to suggest Zoom has muted anything - the image that I was showing above is just a "test audio" thing that Zoom has in it - and it's showing that when I run a test there's no input from the mic at all until I restart the monitor.

While running Zoom, is DPN (Dell Peripheral Manager) or DDM (Dell Display Manager) running in the background? If yes, disable them and retest.

@DELL-Chris M​ Yes, both are running.  I'll disable them tonight and test next week.

OK, both DPN and DDM were disabled overnight on my Latitude, and this morning I've tested the microphone within Zoom and it works fine.

I guess I'll do some more testing to see which of the 2 are causing issues - are there logs that the monitor throws out that can be analysed?

Just started Dell Peripheral Manager at 11:29BST Wednesday

@markdemanbey​ There are logs but I thought they only pertained to when the app itself stopped working.

@DELL-Chris M​ Thanks Chris.  I've enabled and started peripheral manager, with the other still disabled, and I'll see if there's an impact on the service tomorrow morning