Do you have git installed? If not then that’s the most likely reason for that not work. I just re-installed in both SuperCollider 3.9 and 3.10 and it worked fine. Are you using a different version of SuperCollider?
Very strange, can’t seem to find much info on this so not really sure. Maybe someone else will have the same issue and we might find out a bit more. Glad you got it installed either way.