PROBLEM
Note: Esri Maps for Office was renamed to ArcGIS Maps for Office at Version 4.0 (March 2016). As a result, the names of some user interface elements have changed.
After launching Excel and selecting the ArcGIS Maps tab, clicking on the option to sign in to ArcGIS displays a spinning icon, and the login window fails to load.
Esri Maps for Office was automatically upgraded from 2.1.5 to version 3.0.
There are two ways to resolve this issue. One option is to change the ArcGIS Connection to the default ArcGIS Online default URL path. The other option is to add the ArcGIS Online Organization site to Internet Explorer's trusted sites list.
Change the ArcGIS Connection
http://www.arcgis.com
https://www.arcgis.com
Add ArcGIS Online Organization URL to Internet Explorer's list of trusted sites
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