ArcGIS Connection Error suddenly appearing for all users when opening ArcMap 10.4

[Kara_Shindle]

Within the last few weeks, everyone opening ArcMap is suddenly being shown an error about "ArcGIS is currently not connected to online resources."  The Sign In and AGOL options are greyed out in the menu, and looking at the portal connection in ArcGIS Administrator has not helped answer any questions.

Have tried some of the options here with no success: https://support.esri.com/en/technical-article/000012188

Anyone else have this issue?  We're stuck at 10.4 with some 3rd party dependencies right now.