I am connected to the VPN but Google can still see my location. Help!
Some good information about how Firefox handles Location-Aware Browsing is available here and also a bit more detail about the Google Location Services are made up is found here.
Because there is no technically to date to fake a GPS position entry, the only solution you have here is to disable GPS positioning from your device, or to disable it from Firefox using the following procedure.
1) In the URL bar, type "about:config".
2) Type "geo.enabled".
3) Double click on the geo.enabled preference.
4) Location-Aware Browsing is now disabled.
This should give you an extra level of security and privacy. Enjoy!