Removed the module and reinstalled it again, first I had same problems but now (no clue what I did, at least no change in groups and so on) it's working. Probably originally some problem while uploading it....
echo"ONLINE ";
$sql1 = "SELECT * FROM ***_online";
$query1 = mysql_query($sql1);
$num_rows = mysql_num_rows($query1);
echo "- " .$num_rows ." user(s) are NOW online";