Today I figured out why Outlook 2010 and 2013 doesn’t display this information anymore.
Missed conversations and pstn-calls that the user calls out still work fine.
To get it working again uninstall these updates:
KB3114502
** Update 10/2 ***
Yesterday Microsoft released the update.
https://support.microsoft.com/en-us/kb/3114732
It will fix missed calls functionality without UM-role needed!