I am unable to edit a shared Calendar and presented with ‘read only’ message

My husband and I have a shared calendar. He initiated the calendar. When I add an event, and he changes that event, when it comes back to me, I cannot edit the event. It says read only, even though I created the event. This is a problem. We’ve gone into settings and cannot figure out a way to not create a read only event in our shared calendar when he has either changed my event or he initiated a new event. How do we create a non-read only event in his shared calendar?

[Re-Titled by Moderator]