Hi, I'm about to pull the trigger on a Vmix license which is quite expensive for a small YouTuber, and have been testing the software out on my YouTube live stream for the past month. It has been working great up until the past 2 weeks.

My callers aren't able to hear the return Master Audio. It is really important I'm able to have them on the live stream interacting without issues.

You can see there's an issue with my stream here: https://www.youtube.com/watch?v=va99gX0NJMQ and the previous week. However, the stream we did 3 weeks ago worked flawlessly: https://www.youtube.com/watch?v=i34bsfeiT38

We've tried all the troubleshooting recommendations in the help documents:

* Google Chrome browser, Firefox browser.
* Restarting computers.
* Running it on Mac or Windows.
* Changing the audio feed from Master to Bus A etc.
* Making a new vmix call instance.
* Callers changing audio interfaces.

I'm running Vmix version 22.0.0.69 on Windows 10 Pro 64 bit (up-to-date). Intel Core i7 7820x CPU, X299 chipset, 32GB RAM, Nvidia GTX 1080, M.2 hard drives. Internet connected via NBN.

I'm using a PreSonus Studio 192 audio interface which is USB 3 connection. It has worked fine, and need a PRO audio interface as my YouTube channel is all about Music Technology.

Here's the output of the latest log file:

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22.0.0.69 - Call_AudioSourceSelect - 5/10/2019 9:48:13 PM
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vMix.VMIXException: This Audio Bus needs to be enabled in Settings -> Audio Outputs first.
at cd.a(Int32 a)
at mzzzzzl.z(Int32 a)
at mzzzzzl.y(Object a, ToolStripItemClickedEventArgs a)
========================================
22.0.0.69 - Call_AudioSourceSelect - 5/10/2019 9:51:06 PM
========================================
vMix.VMIXException: This Audio Bus needs to be enabled in Settings -> Audio Outputs first.
at cd.a(Int32 a)
at mzzzzzl.z(Int32 a)
at mzzzzzl.y(Object a, ToolStripItemClickedEventArgs a)
========================================
22.0.0.69 - Call_AudioSourceSelect - 5/10/2019 9:51:13 PM
========================================
vMix.VMIXException: This Audio Bus needs to be enabled in Settings -> Audio Outputs first.
at cd.a(Int32 a)
at mzzzzzl.z(Int32 a)
at mzzzzzl.y(Object a, ToolStripItemClickedEventArgs a)
========================================
22.0.0.69 - Call_AudioSourceSelect - 5/10/2019 9:52:09 PM
========================================
vMix.VMIXException: This Audio Bus needs to be enabled in Settings -> Audio Outputs first.
at cd.a(Int32 a)
at mzzzzzl.z(Int32 a)
at mzzzzzl.y(Object a, ToolStripItemClickedEventArgs a)
========================================
22.0.0.69 - DesktopCaptureGDI - 5/10/2019 11:43:35 PM
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Enabled due to DPI scaling
========================================
22.0.0.69 - DesktopCaptureGDI - 5/10/2019 11:43:38 PM
========================================
Enabled due to DPI scaling
========================================
22.0.0.69 - DesktopCaptureGDI - 5/10/2019 11:46:48 PM
========================================
Enabled due to DPI scaling
========================================
22.0.0.69 - DesktopCaptureGDI - 5/10/2019 11:46:50 PM
========================================
Enabled due to DPI scaling

It turns out the problem was at the callers side.
One caller had Windows - was required to change the privacy settings on his camera under Windows Settings --> Camera Privacy Settings
The other caller had a Mac - was required to not use an Aggregate Audio Device (under Audio Midi Setup) - changed it to a single audio interface and it worked fine.

So Vmix was all fine :)

also thanks to Martin for helping solve it :)