If a job is currently assigned to a route, but that the job cannot be completed for any reason, it can be unassigned from its current route, and then re-assigned to a new route.
To quickly unassign a job from the map, or any panel, you can use a simple "drag and drop" method:
Locate an assigned job on the map, in the Routes list, the Route list or the Job Order panel. You can select more than one job in the Jobs list using the check boxes. Begin dragging the jobs with your mouse and the upper section of the Routes panel is replaced with two blue boxes:
Drag the job onto the right UNASSIGN FROM ROUTE box and release. The job is unassigned and removed from the route it is currently assigned to.