Error when launching a related action: No process parameter found corresponding to override [name=pv!document]. Non-parameter process variables cannot be overridden.

Question

I'm getting this error when trying to start a related record action. I've double-checked that all of the process variables in the context are in fact parameters in the process model, and that the data types match. There are no unsaved or unpublished changes in the process model. What else could be causing this error?

Mike Schmitt · Answer

Have you verified that your Related Action absolutely refers to the correct process model? What happens if you comment out that line of the process parameters and then try launching it - does the error still occur? Does the process use a Start Form, and if so, is it configured correctly to the given inputs? 
 Beyond that you just need to try basic troubleshooting steps to see if you can find what the discrepancy is. Add a new PV to the model (temporarily) and try passing that in instead. Change the Related Action to reference a completely different process model and see if the issue follows. Etc.