Stopped (error): X++ Exception: Could not find user at SysWorkflowDueDateProvider

I developed a custom workflow and its setup its corresponding configuration, I was able to submit and everything but ended up getting the following error in my workflow history when the workflow system tried to assign it to user which is the part of managerial hierarchy.

"Stopped (error): X++ Exception: Could not find user at SysWorkflowDueDateProvider-resolve SysWorkflowDueDateProvider-resolveDueDate
SysWorkflowQueue-resume"

I setup the workflow assignment for managerial hierarchy (position hierarchy) which was correctly setup under Human Resource > Common > Positions > Position hierarchy.

Later when I checked the worker association with users I found that under user relation screen the user IDs are wrongly associated with workers. Unfortunately this error message was coming due to wrong or missing worker and user assoication which is a must step for workflow to be processed perfectly.

Workflow always work on Employee (worker) level not on user level so user MUST be associated with the user. I hope this will help someone who runs into the same issue in the future.