Problem with MUC

Hello,

I have a problem on my Openfire Jabber server. In fact, as my client Gajim, when I invite someone to join a conversation to a conversation several (muc?) Does not work.
I installed the package mu-conference 0.8 on my server (downloaded here: http://gna.org/projects/mu-conference/), but it still does not work.

Can you help me please ?

Thank you.