Workflow auto-cleanup timer job does not start

I am testing multiple workflows for clearing workflow history time intervals. Workflow history should be kept for a specified number of days. I have implemented the recommended solutions here

My problem is now I need to check my code to see if the workflow history is cleared after the exact number of days.

I found out that the history of a workflow is cleared using a timer job called "Clean Up Workflow" that runs daily.

But in my case, clearing workflow history doesn't seem to start because in Central Administration> Operations> Timer Job Definitions> Edit Timer Job, the last run time is shown as "N \ A"

Is there anything I can't see here? What should I do to start a timer job?

Update: Checking the SharePoint logs gives the following message: "Update job definition already exists, pending completion of existing update"