Some users may experience no login events in their CAS portal upon initial setup, and this is due to an auditing restriction in Office 365 environment. If you are facing similar issue you may need to login to Office 365 Admin center and enable auditing.
Login to your Office 365 Admin center and do the following to enable auditing:-
Go to "Security and Compliance" under Admin Centers.
2. Next, on the left-hand side menu, click "Search" ? Audit log search and you will see a warning message asking them to Turn on auditing, go ahead and Turn on auditing.
Once you turn on auditing , we should now be able to see login events within a few hours