All Pokémon GO clients (the official game client, maps, various apps) rely on accessing Niantic’s servers via a built in server side API layer. The API layer dictates the minimum app version that can access the data and maps use/emulate a set version API client.
Yesterday, a new version of the API was forced: 0.95.3. As of the time of this writing, none of the community written APIs that maps use have been updated — mainly pogobuf-vnext. As a result, all third party apps that rely on the API are down.