Authentication popup for autologon.microsoftazuread-sso.com:443

aleks_m 

That's what a O365 supporter told me:

1. Open Internet Explorer > look for setting gear option  > Internet options > Security > Trusted sites > add one more url link "https://aadg.windows.net.nsatc.net"
2.  Open the registry editor  and navigate to below path 
3. \HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ZoneMap\Domains\microsoftazuread-sso.com\autologon 
4. Key "https" Dword value should be set to "1" instead of "2"
5. Note: Make sure that you are taking backup of registry file before making any registry changes. 

Please let us know if the given action plan works for you.