In the Explorer iOS app, I am getting an error that says "Missing bing maps key" when opening a map with a bing map as the basemap. The bing basemap works fine on the full website and mobile website and I have verified that my bing maps key is still valid. This has been happening for a few weeks now. What is going on?
I suspect that ArcGIS Explorer app you are using is outdated and using the old Bing Maps SOAP services which were turned off at the beginning of August. I would check with ESRI to see if they have an updated version of the app as they have updated many of their apps to use the Bing Maps REST services which replaced the SOAP services 7 years ago.