How long does it take to install cinemachine? It’s been stuck at “installing” for 20 minutes and still not done.
Try cancel installation, if you haven’t done it, restart unity and reinstall again, if is not installed yet.
Package installer my stuck in some infinite loop or so.
Try uninstall and install again package, this may help also.
Shouldn’t take more than few min.
In worse case, delete libraries folder and reload them again. May take few dozens of min. Maybe upto halve an hour.