When we add user in multisite wordpress it goes to unconfirmed user and will not show if we search user in admin untill user confirmed him from the confirmation email .
so now issue is if you do not have mail setup user will not get the email and you can not find him in admin.
In this case you have two option , one is hard other is simple
HARD : search the user in database and make him confirmed manually. its very difficult for non technical bloggers .
SIMPLE : install plugin “Unconfirmed” and it will show all unconfirmed users of your site in Network admin under user menu and their you will have option to make them confirm user .