Cannot see users under user monitor version 5.6.0

Good day,

We have an issue with some users that are not having internet access because authentication is not working properly. On the Fortigate or Analyzer i can see the log on for a specific user but the user is not matching any rule for thus being blocked by the implicit deny rule. If I check under user ==> Monitor I dont see that particular user. Also if I run diagnose debug authd fsso list the user cant be found.

Please help.

Thanks and Regards