A dimmed or greyed-out event usually means one of two things, and neither is a fault.
Events that have already happened
On iPhone, events in the past are shown dimmed so that today and what is coming up stand out. This is normal, and you can still tap a dimmed event to open it.
A shared event waiting for your answer
An event shown with a dashed border and a ? marker is a shared event your partner has created that you have not responded to yet. Tap the event and choose Accept or Decline. Once you accept it, it appears as a normal shared event.
If you can open the event but cannot change it
If the event opens but there is no option to edit or delete it, it came from a calendar you have synced rather than from Cupla. Those events are edited in the app that owns the calendar. See How do I edit or delete an event?
If your event looks different from any of these, message our support team from the app with a screenshot and we will take a look.