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