Calendar Publishing doesn't work

Hello everyone,

I followed the instructions on http://technet.microsoft.com/en-us/library/jj853046(v=exchg.150).aspx but afterwards I don't see any new option in owa. When I click "Share" I still only see a popup with a blank field where I just can enter an internal mail address. When I enter an external address it tells me I do not have permission to share etc.

=> Is there something missing in the technet article above? All checks they tell me there were successful.

Thanks!
Regards
Christian