I had this issue in the office, but not with all users, and then also came across it at a customer site.
So what happens.. A user has some calendar entries which are accepted by the invitees. The calendar entry and the response documents are in the user’s mail file. All good.
However, when the users opens the calendar entry and clicks on “invitee status”, all the invitees who have accepted or declined the invitation show up as ‘no response’.
It turns out that Traveler “broke” this. From the according APAR:
Event updated on ActiveSync Device may cause attendee status to be lost on server copy of the event. The issue is not seen often with Apple devices, however BlackBerry devices send event updates at regular occurrence, even if the event was not updated so BlackBerry users will see this issue much more frequently.
Starting with Notes Traveler 184.108.40.206 the server has been updated to correctly identify and prevent this scenario from occurring. In order to correctly handle, the server had to be upgraded to handle Active Sync 14.1 and later protocol levels.
If you come across this problem, upgrade the Traveler server to 220.127.116.11 and you’re good to go.
UPDATE: IBM has released an Interim Fix 1 to Traveler 18.104.22.168 and a Flash Alert recommending to delete and recreate Notes Traveler accounts on BlackBerry 10 devices after upgrading Notes Traveler server to 22.214.171.124 or later.
see http://www-01.ibm.com/support/docview.wss?uid=swg21648195 and http://www-01.ibm.com/support/docview.wss?uid=swg21648847&myns=swglotus&mynp=OCSSYRPW&mync=R