It appears that a batch report is not generated if the report is emtpy, i.e. no data was generated to populate the report. In legacy versions the empty report was still saved or emailed.
This functionality is not in versin 2.5.
This behavior is by design. The HTML and CSV reports are created by transforming the XML output. The XML is not created if the report returns no data. If no XML was created there is nothing to transform in order to create the HTML/CSV report file - the transform call fails if the source file is missing or zero bytes.
For subscribers of reports TPAM does send text of "HTML version is empty" (substitute CSV or XML as appropriate for the subscription) rather than sending a zero-byte file. TPAM also sends information if somebody subscribes to a disabled file format.
An enhancement request has been submitted to have empty reports included in the batch. This has been included in 2.5.909.