Both MS Teams and Skype have precisely the same problem - they're trying to "automatically adjust the microphone settings". And this causes the mic in volume gain to be practically minimal => extremely low volume, if not zero at all, while using your MIC
device.
In Skype, you can disable this through the respective setting in "Audio & video" set to Off.
And you can then manually set the gain from 0 to 10.
However, MS Teams gives no such capability. And as the "automatic" setting is on while MS Teams calls are running, you cannot override the MIC gain even through Control Panel > Manage Audio devices > select your MIC and set the "Level" high enough (e.g. 100)
@Microsoft - please enable this capability ASAP in MS Teams.
All other apps in the same laptop (incl. Gotomeeting) work fine - i.e. they allow you to set the MIC gain.