Symptom: When you try to create a new chatroom from the Lync 2010/2013 client, you are redirected to a webpage that shows the following error:
User is not sip-enabled.
Solution: Turns out this is an issue with cross-compatibility between Single-sign on and 3rd party browsers. Make sure you are using Internet Explorer and you should be able to login and manage your persistent chatroooms.
I'm using IE 11 and still getting this when I try to manage persistent chat. 🙁
I can confirm this does work in IE 11. Try adding the pool to your trusted sites and seeing if that works. Also, have you made sure you have all of the latest Cumulative Updates installed for Lync Server?