iCloud Invitations

I have a MacBook Pro. For work, I have a shared iCloud calendar. Whenever anyone sends me event invitations, no matter whether I accept them through iCalendar or the email notification, it rarely saves my response. The few times it does, I have done nothing different. How do I get the iCloud Calendar to save my event invitation responses every time? I have updated my computer and restarted it. All my apps are up to date. My software is compatible with the program.