The Paused Tasks pane shows any tasks that could not be completed. The reason for the failure is shown in the Status column.

Failed Tasks cannot be resumed, and must be deleted manually from the Paused Tasks pane.

If Automatically Find and Relink was unable to find all files in a project, a failed task is placed in the Paused Tasks pane of the Task window. It remains there unless you manually remove it from the Task window (even if you have since found the files through a subsequent search and relink task).