Audacity can't find microphone

I am using Audacity 2.1.3 for the first time with a Windows 7, x64 computer. I have a Logitech USB microphone. Audacity can’t find it. In other respects the mic seems to be operating correctly, for example, I can record audio files with Camtasia. So far as Audacity is concerned the microphone just doesn’t exist.What’s going wrong?

It’s possible you ran them in the wrong order. Audacity checks for connections when it starts. If you started the USB microphone after Audacity started, the microphone will be invisible.

Restart Audacity or Transport > Rescan…