So that's an XLR to USB? What mic is connected? Have you tried a different mic?
All the settings right... You mean like selecting the input to be the USB mic in system preferences/sound/input?
[doublepost=1534256560][/doublepost]
If you have a usb to xlr adapter and other mics work then the drivers seem to be correct. Does the mic that does not work possibly require phantom power?