Audacity will not record after latest OS X update (Mojave) [SOLVED]

Audacity 3 Help Forum macOS
4

Yes. By default, Mojave denies programs access to the microphone (any microphone or other audio input device).
The setting is under “Security & Privacy” settings.

See here for details: No signal from USB turntable (Mojave) [SOLVED] - #6 by SonArc