I have the honor of being selected as speaker for DNUG for three years in a row. This year I will be speaking about troubleshooting Connections.
My session will be June 20 at 14.35
You can see the agenda of the DNUG event here
This happened to me and to a customer. When moving our server to a different machine I forgot to move the credstore.nsf database; while my customer simply did not create it.
In both cases VoP was showing the email correctly but the calendar was empty; as soon as we fixed the issues, moving and creating the db, the calendar started working perfectly.
I have no idea of the relationship between the credential store database and the Verse calendar, but the fact is that without the db the calendar will not work.