If running 17.0 or 17.1 and there is a need for upgrading to NPrinting 17.3. However, in order to keep the Connections and Applications in the database and then restore them for a backup on the target version, if backed up in NPrinting 17.0 or 17.1 the restore will not work in 17.3. That is a limitation and it was described and clarified more under the following link: Upgrading Qlik NPrinting
** To upgrade to Qlik NPrinting June 2017 or newer you must start from any of the Qlik NPrinting 17.3 series.
Additional details regarding the correct upgrade path are as follows:
NPrinting 17.0
NPrinting 17.1
NPrinting 17.1.2
NPrinting 17.2.0
NPrinting 17.2.3
At every step, the same upgrade procedures have to be executed. Back up the database. Stop the services. Run the installer.