Have already created some workflow with this action but now I created a new one and for some reason I receive a error: Error updating document. Expression must evaluate to a node-set.
I even deleted the complete workflow, create a new one with just one content control to update but still this error.
I am sure that the name of the content control in Word and in the workflow are the same.
Someone any suggestions please?
could you post a screenshot of your action's configuration? So the workflow runs fine when you deactivate the action but when activated the workflow fails with the mentioned error message?
Also when odd things happen first thing I check is if the database scheme is correct. If not there might be odd errors when Nintex calls its internal routines.
To check this please navigate to central administration -> Nintex database configuration -> check if there is an update link visible. If there is hit it and try to execute your workflow again.