Great add on. My suggestion is to update your instructions HERE. There are three things that you must do for each usergroup to get this working.
1. You have to check that the usergroup is taggable.
2. In the general permissions, you have to set to yes the "[Tag Me] Tag group:"
3. You must set unlimited or some value in the [Tag Me] Maximum tag/message:.
Or you'd have to change the default install to have these set to start working out of the box.
This is a GREAT add on, but these instructions HERE would help. Thanks for this!