Private forums

I have made a private forum i add ppl to the access thing to "yes". then when they have a look to see if its visible and they cant see it. i put the forum visible and then they cant get into it. only admins and mods can
i then tried uninstallin and reinstalling and the same thing happens.
this a bug or this supposed to happen? plz tell me how to fix. or is there any way of a password thing instead of access.