Advanced Search: Proximity search fails; returns "We could not geocode the destination address."
Proximity search worked fine for me in 4.7.11 and 4.7.10.  Proximity search is available on the demo if you select a geocoding provider (Administer menu » System Settings » Mapping and Geocoding).  

I'd advise checking/changing your system's geocoding settings.  If that doesn't work, please update the question with the settings that aren't working, this is likely specific to your settings.