I think they are installed already…this is why it says no change when you try to reinstall. It’s possible your problem is to do with permissions.
Try this if you didn’t do it on first install.
Uninstall and run the installer again…Tick the “install for all users of this computer” check box.
Note that Acoustic Agent is not a VST instrument, it’s loaded with certain presets in GASE and can be tricky to find at first…see here for an example method: