I Have a webmap that I can successfully use offline with Collector. Up until today, I was using the standard esri Imagery with Labels basemap. My offline areas were created just fine.
Today, I switched that basemap with my own ArcGIS Server based web-mercator tiled image basemap for our county. The web map comes up just fine in AGOL, the settings for the map still show that it's good to go for offline use but when I go manage may offline areas, that new basemap layer doesn't get added to the offline area, only my points, lines and polys layers (operational layers) are in there. Can't I use my own basemap tiled layer hosted through my own ArcGIS Server for offline areas? If so, what am I missing with that?