Can someone please help?

Can someone help me? I'm trying to ban players but I can only ban guests.

The script i'm using is..

if(keyboard_check_pressed(ord('B')))
{
if(gms_self_admin_rights()) {

name = get_string("Username", "")
reason = get_string("Reason","")
days = get_integer("Days",10)
player_id = gms_other_find_by_name(name)
gms_admin_ban(player_id,reason,days)

}
}

In the players step event