2 - Version of NPrinting you are using may be out of support already - I suggest to stay with the up to date version
3 - Are you running supported configuration: meaning (given how old NPrinting you are using) is your NPrinting version equal or newer than Qlik Sense - this is compulsory for it to work properly and is officially documented on https://help.qlik.com
4 - Can you reload metadata, edit template and click "Verify Entities" - is the object error refers too still in the app or maybe it was from your Qlik Sense app? Or maybe there were changes done to this object?
Having answers to the above will help us identify what the problem can be.