I don't have nprinting 17 version. would be able to raise ticket with qlik support team.
also can you share more detailed level log (log path : C:\ProgramData\NPrinting\Logs) extract recent error & share it.
some more details required:
what is you app file size?
also check below points,
1) is this issue occur 1st time after installation? if so try to clean/ re-install with latest version
2) have you tried to restart Nprint services? tested the app?
3) app located same server folder/different location? try to do simple report & test it out
5) only this issue occurred in this app? what about other app works?
6) did you applied any patch/upgraded to latest version?