If a workflow is unable to be started, and the template is saying that it requires an update, this means that there is at least one step that is assigned to a user that has been removed from the system.

This workflow template will need to be edited, and any steps that are marked as "Not assigned" should be reassigned to an active user using the edit button to the right of the step. You should be able to edit the template from the Workflows > Manage Templates page here.