If a job was prematurely marked as complete, you can quickly "unfinish" the job. 

On the web portal, go to the job details page of the job you need to adjust. 

Click the arrow icon above the 'Finish Job' tab. 

A window will appear for you to confirm the action. Click 'unfinish job' in the bottom right. 

The 'finish job' tab will now be cleared for you to hit at the right time.