Oh. I'm still using MacOS 10.14, so there's an official up-to-date version to download from the Lilypond site, and I think I'm using a two year old version of that. (I am very slow to update the OS on my main work machine, usually just ride out the major version it came with until I update to a new machine; and since I was working on a book in Lilypond, I wasn't in a hurry to update it, either.)

Sorry I can't be of more help immediately!