Can you post the task log, or at least the errors you are receiving in the task log? If the errors indicate that the source document was not reloaded, then you'll need to provide the document log as well. By default, the task logs are stored in %ProgramData%\QlikTech\DistributionService\1\Log\DateOfTask\NameOfTask. If you have configured the QDS Application Data Folder in a different folder, you can check the location by looking in the QMC > System > Setup > Distribution Services > QDS@ > General tab.
If document logging is enabled, it will be stored in the same directory in which the QVW file is housed. If document logging is not enabled, you will need to open the QVW file in QlikView Developer, click Settings > Document Properties > General tab and ensure the Generate Logfile checkbox is ticked. Then run the reload task so that the document log is generated.
This will help in determining the cause of the issue you are experiencing.