Hello! This is a strange bug we'd encountered a few years back and which we confirmed still affects the new version of the AVD web client.
The issue we encountered can be reproduced as follows:
Navigate to RDP Properties > Device Redirection on your host pool. Set Audio Output Location to "Do Not Play Sounds."
Device redirection (remote desktop virtual drive, remote desktop virtual printer) functionality will break in the web client. To workaround this, we set audio output location to "play sounds on the local computer" instead, and it began functioning as normal.
This issue is also described here:
https://www.reddit.com/r/AZURE/comments/svk1pw/anyone_run_into_issues_with_the_virtual_redirects/