"Allow the authentication only on this Microsoft Windows host" - doesnt work

after creating an account, on the tab Accounts, the windows Option:
Allow the authentication only on this Microsoft Windows host - if a servername is wirtten in it, the user cant login. not to the Host
i tired:

  • 172.xx.xx.0/24 = failed
  • Servername = failed
  • Server IP - failed
    anything i am doing wrong
    as soon any written value there is removed, login is possible again. any hints ?