I run the setspn command for specific user on Domain Controller.
C:\>setspn -s example/username.companyname.com username
Checking domain DC=companyname,DC=com
Registering ServiceprincipalNames for CN=username,CN=Users,DC=companyname,DC=com
example/username.companyname.com
Updated object
And immediately can see result in console.
C:\>setspn -L username
Registering ServiceprincipalNames for CN=username,CN=Users,DC=companyname,DC=com
example/username.companyname.com
But it never affects this user in "Active Directory Users and Computers".
His attribute "servicePrincipalName" is not set.
Maybe there is some kind of cache?