Something similar is happening to us. We created a webMap in ArcGIS and a Web Application (using application builder.) as well. When we look at the map or the application, the layers show up find. When looking at the map through the [ArcGIS] Explorer App from Android, the points do not show up. In this case, the grouped symbols seem to be showing up in the map, but the non-grouped ones are ignored. Furthermore, the legend does not show correctly as it shows only symbols for non-group items.