Hi, I am a Microsoft user just like yourself and I will try my best to help you as much as I can today.
If you're unable to mute or unmute during Microsoft Teams calls on your Android device, you can try a few different solutions:
Ensure that the Teams app is updated to the latest version. Outdated versions can have bugs that may cause audio issues.
Check the app permissions for Teams on your Android device. Go to Settings, then Apps, and make sure Teams has permission to access your microphone.
Try clearing the cache for the Teams app. You can do this by going to Settings, then Apps, selecting Teams, and tapping on Storage. From there, you can clear the cache.
Restart your device. Sometimes a simple restart can resolve unexpected app behavior.
If you are using Bluetooth headphones, make sure they are properly connected and that Teams is set to use them as the audio output and input device. Misconfiguration can lead to such issues.
These links have more information on similar issues faced by others:
https://answers.microsoft.com/en-us/msteams/forum/all/i-cant-unmute-on-teams/767cbd22-b9d6-40a6-9fcc-498a43d7a19f
https://answers.microsoft.com/en-us/msteams/forum/all/how-to-fix-the-problem-on-muteunmute-the/57a56f52-0900-4f1e-bfe3-87428f1040e2
https://answers.microsoft.com/en-us/msteams/forum/all/unable-to-unmute-in-teams/a4478e5c-84e5-4438-9b33-538a4b009241
See if that helps! Please let us know if you have any questions. Microsoft Support is available for further assistance if the issue continues.
Best regards
Deeply