Audacity won't recognize preamp

Go to Apple (menu) > System Preferences > Sound > Input. Does the Solo show up there? If not, figure out why.

While you’re in System Preferences, go to Security and Privacy, click the Privacy tab, click the Microphone is the list on the left and make sure Audacity is checked. See https://forum.audacityteam.org/t/no-recording-level/51788/1

Now start Audacity. Can you select the Solo in the Device Toolbar?

By the way, the latest version of Audacity is 3.1.3 and is available here.

– Bill