A remote room cannot fix a microphone that the computer does not receive. Test the local input first. This separates a hardware problem from a browser permission problem and saves the guest from waiting through the wrong checks.
Make one local recording
Connect the USB microphone before opening the browser or desktop recording app. In the computer's sound settings, choose that microphone as the input. Speak while watching the input level. Next, record ten seconds in a local recording tool and play the file back through headphones.
If the file is silent, check a physical mute switch, the cable and the selected input. Some microphones appear as both an input and an output device. Choosing the microphone's headphone output does not prove that its input is selected.
If the recording is clear, open the remote room and select the same named microphone there. Device names can be similar, so compare the complete name rather than choosing the first item containing USB.
Keep the test simple
Close other recording or meeting tools during this check. Reconnect the microphone once if the device list is stale, then reopen the recording page. Do not change the network, browser, microphone and cable at the same time; that makes the useful result hard to identify.
A USB hub is another possible part of the path. When practical, compare a direct connection with the hub connection using the same ten-second sentence. Keep the working path for the interview. After a successful test, avoid unplugging the microphone while the room is active. A changed device can require a new selection or permission check.