Steps to update the ArcGIS Connection manually (make sure the Portal for ArcGIS that user is updating it to, is valid and working):1. Navigate to the following configuration file (<a href="file:C:/Users/" target="_blank">C:\Users\</a><Current Windows User>\AppData\Roaming\Esri Maps\ESRI.ArcGIS.Mapping.OfficeIntegration.Excel.dll.config)2. Update the above file so that the value for ArcGIS Connection is pointing to a valid Portal for ArcGIS path:<add key="ArcGISConnection" value="<a href="http://www.arcgis.com" target="_blank">http://www.arcgis.com</a>" />OR<add key="ArcGISConnection" value="a valid Portal for ArcGIS URL" />3. Save the file, and open Microsoft Excel.4. Attempt to either go to the Esri Maps Tab or view the Esri Maps Configuration at File > Esri Maps.5. Confirm that no crash occurs.