I would be willing to wager that I know what the problem is ;)
The list of channels listed on the LOGIN page is determined by what the Guest user is able to access (which makes sense because Guests are not yet authenticated ;))
Therefore if you update the array of your guest user to include all of the channels you should see the full list.
Default configuration:
// Default guest user (don't delete this one):
$users[0] = array();
$users[0]['userRole'] = AJAX_CHAT_GUEST;
$users[0]['userName'] = null;
$users[0]['password'] = null;
$users[0]['channels'] = array(0);
New configuration (to see ALL channels):
// Default guest user (don't delete this one):
$users[0] = array();
$users[0]['userRole'] = AJAX_CHAT_GUEST;
$users[0]['userName'] = null;
$users[0]['password'] = null;
$users[0]['channels'] = array(0,1,2,3,4,5,6,7);