Missing notifications in my iCal

Hi

We are three people how share a calendar on icloud for a project we are doing. I started the calender and invited the two others. Now the problem is, that I don't get any notifications in my iCal or on my iPhone when they change/update/add notes to our events. It is a bit annoying, because then I might not see the notes we leave for each other. Can somebody help me on how to make it work. On my iPhone I have the "new invitation alerts" on and also "shared calender alerts".