Why can't I get the WP "Tweet This" plugin to work?



I have the WordPress “Tweet This” plugin on 5 web sites and I have made 5 Twitter Developer Applications (https://dev.twitter.com/) for each of these sites to use with the “Tweet This” plugin. I’m sure that I’ve followed the instructions on the plugin when making the 5 applications to get the right codes to copy and paste onto the plugin to make it work.

Only none of the “Tweet This” plugins work on any of the sites. I always get this error:

“Tweet failed. Twitter returned HTTP 401. Check your OAuth settings and re-save this post to try again.”

The checker for the OAuth settings on the plugin always confirms that the authentication codes are good.

Why is that, what am I doing wrong and what can I do to get this plugin to work?


PS Is there a WordPress plugin for automating Twitting that works?
PPS Is there a WordPress plugin that works like and as good as the automated submissions to Yahoo! Updates, Twitter, Facebook, LinkedIn, Messenger Connect on the WordPress.com sites?