If you go to Project management and accounting > Setup > Project Management and accounting workflow and you select any workflow and hit Edit and you get an error stating
“Error executing code: FormRun (data source) has no valid runnable code in method ‘new‘
Try to to locate the form that is failing to launch in the AOT. In this case it will be ‘WorkFlowEditorHost’. Make a small change to the form, compile it and then delete the change and recompile.
Try now to see if you are able to edit the workflow after this.