We have a user with a recurring meeting, with multiple participant. For one instance of the meeting, it is appearing on some participants' calendars but not others. For the ones that it is not appearing, I looked through their email, and they seem to have received the pertinent meeting request and modification messages. When new modification messages are sent, if the users select the message and click "Accept" in the email interface, still nothing appears in their calendars.
Any thoughts are appreciated - I'm not even sure how to troubleshoot this further (we've only been on Zimbra for a few months). I searched the bugs, but didn't find one that I could specifically match to this.