I've had a map up for about a year and it has been working fine. Recently the URL changed for one of my basemap layers - this basemap layer is hosted externally. When I got in to the launch the map viewer to update the basemap URL none of my layers are showing up. As expected, I get a popup saying the basemap can't be loaded so it'll use the default basemap, but then none of my layers show up and it reverts back to the default extent. It's like starting fresh from a brand new map. not good. I can launch the map fine in ArcGIS desktop, but it will not load in the ArcGIS online map viewer.