Problem with authorized user login !

hi, i’m using a hotspot fasilities in mikrotik
but i’ve got a problem when i try to use any authorize login in this system
for first user it will view a login page to authorized the user login..
but when 2nd., 3rd .. etc use that facilities,
a login page won’t appear anymore and all user after 1st user will be able to connect internet without authorize !!!
anyone can help me !?