Lost workflow due to unassigned position

A user has entered a service entry sheet which has to be approved by their manager. However, the workflow couldn't find an agent to forward the request to because the manager position was not assigned to a user name. HR has rectified the problem and now I need to restart or rerun the "get next agent" task to pickup the manager and forward the request for his approval. I'm not sure how to restart a task (I only know how to restart the workflow after an error using SWPR transaction). What should I do?

Unfortunately, if the "get next agent" step has executed then it can not be re-executed (unless it is in a loop). As a workflow admin, why don't you just forward the work item manually to the correct person? They will then process the work item and the workflow will continue.