is there a way to do a simple reduce and distribute (or keep the application in its folder) by a task in QMC and (now the important) keep the hole script in the application. I know the reduce part inside the application but they want it scheduled.
It could be that. Do you use Section Access (within the QV document) in addition to a simple reduce? That can sometimes cause conflicts if not configured properly, e.g. you need to give the QlikView service account ADMIN rights on document level.
Otherwise if the field and value that you are using for the simple reduce exist, and the QV service account is allowed to see them, then I can't think of any other reason it wouldn't work. I would try adding a new tasks and testing it again, just in case something has been configured incorrectly. Have you enabled full logging and checked the log files for clues?