We have an issue with internal staff members. We added a staff member who's log-in UPN is different from default reply address SMTP. When the staff member has been added, user gets e-mail, but when opening Bookings app, user can not access the Booking page. It will show only this default webpage with this big "Get It Now" button.
Anyone had the same problem?
I am trying now to change default reply address to same as UPN and then try to add the staff member again. It seems that it takes time until Booking syncs the changes with Azure AD.
After I changed SMTP address to same as UPN, then everything works. User can access the Bookings page "back end" and can administrate everything. So that's not very good system from Microsoft, to use Primary Proxy Address to put as authentication when taking from Azure AD rather than use UPN for that.