I just added two expansion packs, the Metro Heights and the Rock Essentials and they are not showing up when I launch GA5 in Cubase Pro 11. Where should the files for these packs be stored?
They are .vstsound libraries and you can put them wherever you like and/or have the storage space available.
Use the Steinberg Library Manager under Details for the item it should show you their current location and let you change it if you want. If you don’t see the Pack in the Library Manager that means it isn’t registered (this is probably the case if GA isn’t seeing them). If you’ve misplaced the .vstsound files most likely it is in the default download location set in the Download Assistant or wherever you specified at the time of downloading.
They are not like Preferences that are saved in a specific location, you decide where they go. Worse case use Windows search to find them. Then move the files to be with the rest of your Steinberg content. If you double-click on a .vstsound file it will register itself and scan the file’s current location and register anything else it finds that’s new.