However, I’ve never been able to get quarks to work automatically in Windows. The git subprocess returns with an error and then sclang hangs. (At least that was the case a couple years ago; I’m pretty sure it hasn’t changed much since then.) There are already bug reports filed.
Then I would re-install SuperCollider, and if that doesn’t work let me know. Also reboot.
If none of this works, is the “recompile class library” button greyed out in the Quarks window?
If you navigate to: C:\Users\<you>\AppData\Local\SuperCollider\downloaded-quarks\quarks\ and open “directory.txt” what’s in it?
I have had this problem twice last year, and there is an issue on github: