FYI – https://support.citrix.com/article/CTX253754

User called to say Audio/Video devices were failing to pass through to MS Teams. Under Settings > Devices listed “None” across the board:

Checked the local workstation and found the HDXTeams.exe was not running (should start automatically when Teams in Citrix launches)

Logs are here: %userprofile%\AppData\Local\Temp\HDXTeams

Refer to : https://discussions.citrix.com/topic/407820-ms-teams-not-pulling-through-audio-devices/page/2/

Solution: I had to disable built-in microphone and speakers – one or both of these were the problem: