Below are several questions in order to get some more information on this issue:
1.Are you using Teams for Windows?
If yes, would it work for you in Teams on the web?
2.What device are you using?
Can you see if it is listed in Teams Settings>Devices?
If yes, would you see the device during a call/meeting in More>Settings>Device settings?
Please make sure you have the correct device selected in Speaker.
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