While trying to setup a new Proximity facet in FacetWP I kept receiving the following error when trying to get the suggested search to appear.

This API project is not authorized to use this API. Places API error: ApiNotActivatedMapError

I went ahead and enabled the Maps JavaScript API as instructed by Google’s instructions, however this did not solve it.

Enabling the Places API however, solved the issue. (NB. During debugging I also enabled the Distance Matrix API and the Geocoding API, but not sure if they helped).