Map Layers from Another REST Endpoint Unavailable - No Layers Show

This morning, it was found that our GeoCortex apps were not showing any layers and a warning splash screen would say that some layers were unavailable. The layers that were unavailable were from the a county's REST endpoint but it would result in none of our layers drawing. These layers from the county are also our basemaps.

 

 

Since the layers that were unavailable were our basemaps, is that the reason that none of our hosted layers would show? How do we resolve this issue so that the next time the county's layers are unavailable, we can have a back-up basemap to result in all of our hosted layers showing.