I finally got the "My Highlights" project opened up again after noticing that there were several issues opened up on GitHub. I had thought no body was using it so it hasn't been a priority before.
I resolved two issues, not being able to import highlights (kind of essential) and not being able to see the toolbar icon. While solving those issues I created some other problems with the build pipeline that I got to solve too!
The latest version of My Highlights (1.16.2) should be working again. Feel free to open an issue on GitHub if something isn't working right and I'll watch it more proactively!