Do you happen to use Webex on macOS? If so, have you ever been on a call/meeting, finished that meeting, then immediately get a call/meeting request and join that one? But, when doing so, you can hear the person fine, but they cannot hear you?
And, the correct input/output is selected. Additionally, you change to multiple other bluetooth devices, and even a wired device, and still they cannot hear you.
And, the correct input/output is selected. Additionally, you change to multiple other bluetooth devices, and even a wired device, and still they cannot hear you.