I installed the plugin and generated the authorization keys several weeks ago on a client website here:
My client posted an article April 15th and it was not tweeted. When I look at the post, this is the error:
Tweet failed. Twitter returned HTTP 301. Check your OAuth settings and re-save this post to try again.
I took the option to clear lock updates and the plugin returns the message that there are no locks to clear. I then updated the post, but it still doesn't tweet it.