If an official chooses to decline an appointment, the status against the fixture will update to declined.
Hovering over the declined status will provide the reason the fixture was declined.
You can reassign the declined fixture to another referee by clicking the officials name to amend the official assigned to that fixture.
Once the officials role has been reassigned, the official will no longer appear on the Assignment Modal if they are now un-available.
Remember: The default Status filter in the Appointment View will only display Declined fixtures if they have yet to be re-assigned. In order to see a history of all declined fixtures, you must explicitly set the Status filter to Declined.