Right, it should be lon instead of lng for the index field to pick up your data correctly. For reference, there are also others ways to index geo_point data, but lng for longitude is not supported: https://www.elastic.co/guide/en/elasticsearch/reference/current/geo-point.html#geo-point.
Looks like the lng data is just ignored by the geo point index, this is why nothing shows up. You have to re-index your existing data with the correct field names, then it should work.