Support Team replied the topic: Can't get the workaround for Joomla 1.5 to work
AutoTweetNG v6.5.1 is a whole different version than v4.12. You can only check it as a reference.
We don't support v4.12 or Joomla 1.5 any more, so we don't have performed the changes. In theory, only the Twitter API v1.1 new library, and the new Urls are required; but in practice, you might have to check other subjects.