How it works? If someone types keyword/location field, and select a distance value, the address will be geocoded to latitude and longitude and all properties that are in the selected radius of that point are returned in search results.
If you want to enable Radius Search in your theme, you need to create another Google Maps API Key without any key or domain restrictions. This key will be used on server side geocoding and it won’t be public.
Once you created new API Key, paste it to Listeo Core → Map Settings → Gooogle Maps API key for server side geocoding
How to verify if Geocoding is working?
Make sure you key is properly created (not restricted to domain and all APIs enabled). Open following link and add your API key at the end of URL: https://maps.google.com/maps/api/geocode/json?address=%22New%20York%22&key=ADD_YOUR_API_KEY_HERE