Wav file preview is not working anymore
In the previous versions, it was possible to listen to audio files inside channels or chats without downloading them. A recent update (in June 2020) has broken this feature for .wav files.
same here. I tested renaming the .wav file to .asf and the in-line works, so it's not a codec issue.
It's not an officially supported extension as per https://support.microsoft.com/en-us/office/file-types-supported-for-previewing-files-in-onedrive-sharepoint-and-teams-e054cd0f-8ef2-4ccb-937e-26e37419c5e4 however .WAV still works in sharepoint/onedrive online, just not Teams.
Most voicemail systems only allow .WAV files and it was really a great system to be to able to put the voice messages into a channel for the team to action.