The service account for NPrint does not have access to the QVW you are attempting to load. Grant Access to the document.
This can be via Section Access Management or by making the User a member of the “QlikView Administrators” or “QlikView Document Administrator” group and re-publish the document.
Please note that if you create a new service account and change the Service Account for NPrintingService and experience the above error message. NPrinting will not function correctly until documents are republished. Republished documents will have the required rights to access the documents.