the ods documment created by iReport dont open in version 5.4.X of libreOffice, only in minors versions.
Open iReport 5.6.0, and create new simple report.
Put anything in report (static text for example).
Alter the preview to use "Open Document Spreadsheet (ODS)".
Click in preview (Button near XML).
When the report open by libreoffice the error occours. "Invalid format", but if you use the version 5.3.6 of Libreoffice, the document open normally.
I have attached a document created for example.