Declined MacOS calendar invites continue to show

Declined MacOS calendar invites continue to show in the MacBook calendar only.

I have declined an event sent out through Outlook. The declined event is not visible in Outlook. The declined event is not visible in my IOS calendar. The declined event is visible on my MacBook.

The event shows and there are no buttons to decline or edit or delete the event.

I have "Show declined events" unticked in the View menu.

I'm wanting to use the app but I have many event invites making the Calendar app unusable.

Help!