iOS calendar doesn't sync in background The iOS calendar app doesn't sync iCloud calendars anymore.

Example: I add calendar events on a mac, which uses the same iCloud calendars, and add a notification for in 5 minutes. In the past, my iPhone would notify me about this event though the set notification. This doesn't happen anymore as I now have to manually open the calendar app on my iPhone in order to make it sync the calendar events.

How can I fix this?
So the actual solution was to go to:

Settings &gt; Calendars &gt; Accounts &gt; Fetch New Data &gt; [My Account name] &gt;and here tap on "Push".

Selecting "Push" in
Settings &gt; Calendars &gt; Accounts &gt; Fetch New Data
was not enough.