That’s very weird! So you get the error message when you run faircamp --preview after editing your .eno?
And is there one .eno in your “Artist Name” folder, and another .eno in each “Release” folder?
If you’re on Mastodon or similar, I recommend the #faircamp tag, loads of us try to help out on that! There may be someone more familiar with faircamp on Mac & brew who can help…