Why does the author account creation form say 'registration has been closed'?

When trying to create an author account, the form shows a message saying "registration has been closed." What causes this, and how can it be resolved?

This message appears because a deadline has been set for the author account creation form. When the deadline is reached or set to a past date, the form automatically displays the registration closed message to prevent further account creation. 

To resolve this, an event administrator can remove or update the deadline for the author account creation form in the form settings. Once the deadline is cleared or moved to a future date, users will be able to create author accounts again.