I have installed the Classic Systray from the Webupd8 Gnome3 PPA. I use Gnome-Shell 3.4 with Precise, and this package is available for those. The problem is that I cannot enable it in the Gnome Tweak Tool. When I enable it nothing changes, and when I close Gnome Tweak and restart it it is disabled again. If I go to extensions.gnome.org and try to enable it from there the same happens. The weird thing is that Classic Systray is still in the list when I remove the package. Isn't it normal that the extension will disappear in the list when it's deleted? And I have tried to reinstall it many times, but nothing seems to work. Does anyone know how to fix it?
Have you tried removing it manually? Find the folder in /usr/share/gnome-shell/extensions/ and delete it. Then, try to reinstall from extension.gnome.org