Have you read Windows 10 Audacity Internal PortAudio error or no devices Have you seen if you can obtain Windows 10 audio drivers from the web site of your computer manufacturer?
What is the make and model number of the mic? What do you mean by it leaves your mIc on ?
Try Transport > Rescan Audio Devices at the top of the Audacity menus. You should use that when you add or remove external devices while Audacity is open.
Gale