Are you on the latest version of NPrinting Server, Engine and Designer?
If no, it is highly recommended to also upgrade to the latest version of NPrinting (both NP designer and NP server must be upgraded together to the same NP version) to mitigate issues with the NPrinting Designer and NP Server and to leverage all bug fixes and performance enhancements.
NOTE: Virtualized desktops where NPrinting is installed are not supported ie: Citrix deployments
Possible corrupted NPrinting Designer and or MS Office Installation:
Uninstall the NP designer
Make sure to download the NP designer software version that matches identically the version of the NP server that it is connecting to
Uninstall Microsoft Office then reboot
Reinstall Microsoft Office and then NPrinting Designer followed by rebooting the desktop computer again.
Ensure a supported version and 'Licensed' version of MS office is available for installation
NOTE: Virtualized (Citrix) and or cloud versions of MS office are not supported by any versions of NPrinting
Install a supported copy of Microsoft Office
Install the NPrinting Designer
Retest...issue should be resolved
Complete removal of Microsoft Office & NPrinting designer
USE THIS FOLLOWING STEP WITH CAUTION BEFORE PROCEEDING: once removal is completed, delete and recreate the Windows user profile of the windows account (save all desktop files, document folder data, public folder data, documents folder data before proceeding with this option.
Once the new profile is created, install a supported version of MS Office and NP designer then reboot and retest
NOTE: Deleting a windows user profile from your computer will result in loss of all files and folders associated with this user profile deletion. Ensure to backup desktop profile files and folders before proceeding