I geocode all my properties before I import them and then you map that field in WP ALL Import.
You cannot put a town name in the property_long & lat fields they must be actual longitudes and latitudes. Make sure to include the “-” symbol on the longitude. It works fine if you do this. I’ve done this for 11,000 properties with this theme.
I’ve experimented with a few different geocoding services. But am now using an node.js NPM script. http://www.geocod.io is a pretty good service.