I am able to record into my mic, into my Scarlett solo interface, and onto audacity.
I see the wav form.
I can hear my own voice in headphones my mic.
I can export the audacity file to .wav and hear it on other players on my computer - so my interface and headphones are working.
But in Audacity the playback is silent in my headphones, and the green sound bar is moving upon hitting play, as if sound is happening.
Nothing is muted.
Please help! I am in the middle of a job and it’s due ASAP.
What version of Audacity? Which version of macOS?
Make sure Audacity’s playback volume is turned up. With Audacity 3.2.0 and later the playback volume slide is integrated with the playback meter. In earlier versions there is a separate toolbar for the volume controls.
– Bill
Newest Audacity and Monterey on Mac. By going back to the older version of Audacity we were able to see that the volume bar somehow was turned down but my audactity-tech-savvy friend and I both noticed that this is not very clear to see or find on the new version of Audacity, maybe that should be in the next fix 
I am glad to hear you have this sorted.
Please create a New Issue where the developers are likely to see it here: https://github.com/audacity/audacity/issues, and share your concerns and your suggestions for improving Audacity.