Create Report on Task

Hello,

I want to create a report on a task object, but I get an Aucotec.EngineeringBase.Client.MethodNotAllowedException.
Here is how I tried it:

 var reportTemplate = _eBApplication.ActiveProject.TemplatesFolder.FindObjects(filter,SearchBehavior.Deep).FirstOrDefault();

 var obj = _eBApplication.Selection.FirstOrDefault();

 var pathToStoreReport = _eBApplication.ActiveProject.DrawingsFolder.Children.FirstOrDefault(x => x.Name.Equals("Temp-"));

 var testreport = obj.CreateReport(reportTemplate, pathToStoreReport);

The object I execute the assistant on is a Task of Type "Wartungsmaßnahme" (MaintenanceTask) in the ExecutionTasksFolder.
When I run the assistant on other objects it works.
Via the UI I can create the report on the task.