For Microsoft PowerPoint, in the File > ArcGIS > Advanced ArcGIS Configuration section, instead of using 'https://myPortal.example.com/portal/resources/arcgismapsforoffice/2021.2', use 'https://myPortal.example.com/portal' for the ArcGIS Enterprise connection from PowerPoint.
When the ArcGIS Enterprise URL, 'https://myPortal.example.com/portal' is entered, a message is displayed stating that "ArcGIS Connection has been changed. Restart your PowerPoint". Click 'OK' in the message window. Restart PowerPoint. Navigate to the ArcGIS tab, click 'Sign-In', and the Sign In window displays.