I cannot add basemap and the global shows ArcGIS not connected. I cannot solve it according to https://community.esri.com/groups/technical-support/blog/2013/04/01/having-issues-adding-arcgis-onli...
can you login to your esri account?
The link doesn't work, it is appearing as text only.
Hey Jack,
It sounds like you're not connected to an active Portal/ArcGIS Online organization. Try launching ArcGIS Administrator on your machine and check the Portal connections.
Use ArcGIS Desktop with your portal—Portal for ArcGIS (10.5.x) | Documentation for ArcGIS Enterprise
-Josh