Have you changed anything in your configuration? You can go to your NP client and load your NSQ file and see what is currently in the schedule. I am assuming that you have had a working model up to now. Do you have data that has been reloaded?
If you can't find anything wrong, then you might try restarting your service or the proverbial when all else fails, reboot your Nprinting Server.
If all of this fails, then submit a help ticket to Qlik Support team
Could you please try the following (just a hunch):
1. Open QlikView NPrinting Server
2. Stop the service
3. Remove all the NSQ's and Folders from the list
4. Close QlikView NPrinting Server
5. Browse to the folder %ProgramData%\NPrinting\Monitor\
6. Rename Schedules.xml to SchedulesOLD.xml
7. Open QlikView NPrinting Server, add the NSQ's and Folders to the list & check the Monitoring Tool
Let us know the outcome.