I know its annoying when the Lync Client lowers the volume of the Receiver when a call comes in, in fact it lowers it all the way to zero. This of course means no sound in the VDI session which also means no sound for the Lync Client.
“When a Lync call starts, Receiver reduces the volume on the device. Use the device audio controls to increase the volume.” This like a silly solution and doesn’t work in an enterprise.
The workaround for this is to delete your Tracing Files from both your VDI Connector “Wyes Terminal” / Windows Terminal with Lync Plugin;
Inside your VDI VM, you also have the same files, please delete them as well.
1. Signout from Lync Client
2. Delete your sign in info.
3. Kill the Lync.exe process
4. Delete the files and folders within the Tracing Folder. Please don’t delete the entire Tracing Directory.
5. The registry got mixed up with lots of Audio Devices and some Reg Keys available here related to Audio was set to 0 HKEY_CURRENT_USER\Software\Microsoft\UCCPlatform\
Deleting the UCCPPlatform Key, reboot fixed the issue
Hope this will help you to rectify your problem.