Which log(s) are you consulting? You'll want to review the QlikView Distribution Service task log of the failed reload task, along with the document log of the QVW file associated with the failed task, not Windows Event logs. 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.
You should then review the task log - scroll to the bottom and read upward until you come across "Error." If you see something similar to "Source document did NOT reload" then you need to review the document log for the error.
Once you have these logs, post them here.