How to run workflow when a process is finished?

Hello,

I have a stage field (text field) that I was to update to the word "Closed" whenever a process flow is "finished". I currently have a workflow that runs that should updated the field when the last stage of the process "exits" (have "on exit" checked in process flow) which also finishes the process but the field is not updating.

If I run the workflow manually it does change.

Any help would be appreciated. Thanks!