Citation fields wiped out after closing document

I have installed JabRef 5.1 and I am using it with LibreOffice 7. I managed to insert the citations and all worked well. But when I re-opened the document, all the citation fields have been converted in plain text, thus I have lost all that I inserted and I need to re-insert all the references?
Why has this happened? Can I keep the Jabref fields in an L.O. document?
Thank you

Are you saving in the native odt format or are your saving in another format? (e.g. doc/docx)
It might also be an issue with version 7. We did not yet test with LO version 7.

Thank you, that was it. The document was a docx, now as an odt it stores the fields correctly,