Hi KL_Mast,
According to your description, when you export the report to Excel, all data are exported, but data rows are missing in CSV render, right?
In Reporting Services, DataElementOutput controls which report item data appears when a report is rendered by a data-only renderer (CSV or XML). If we set the value of this property as Auto, data renderer will think which should output. If the item is a
text box with a constant value, such as a label, the item does not appear (NoOutput). In your scenario, please set the value of this property to Output, the data renderer will obey the setting, export the data element.
If issue persists, please try to create a simple report without any other settings, check if data row will missing when exporting to csv.
Reference:
DataElementOutput Element (RDL)
If you have any question, please feel free to ask.
Best regards,
Qiuyun Yu