I have a Web Mapping application on AGO that contains 3 services that were all published initially to ArcGIS Server. Users of the Application are reporting that 2 of these services aren't loading when they open the app - they get the "The Layer cannot be added to the map" message. the rest of the map loads and displays as expected.
All 3 services were published from maps using data from the same Enterprise GIS. All 3 are shared with Everyone. Other than the content, all 3 services appear identical.
EXCEPT that when I open the Overview for the web map that feeds the Web Mapping App and click on these layers, one of them leads to a secured page, while the other 2 take me to unsecured pages. The 2 layers that won't load (surprise) are the ones that take me to unsecured pages.
What determines whether an item's Overview page is secured or unsecured? How is it that 2 of these services are different? ANy thoughts would be appreciated.
Update: I tested this using Firefox and all the pages were secure. Cleared my cache in Chrome and everything is back to secured there as well.
Still no closer to understanding why 2 of these services refuse to load and the other works fine.