If you wrote your document in Google Docs, this tool cannot help you, and the reason is worth understanding rather than working around. Google Docs keeps revision history on Google's servers, not inside the file. The .docx you download is generated fresh at that moment and carries no editing history at all.

So a Google Docs export will show up here as a document with no writing history. That is a correct result about the file and says nothing about you.

What does work for a Google Doc

• The document's own version history, in File → Version history → See version history. It is the authoritative record and it lives in your account. Open it, and take dated screenshots showing named versions across the period you were writing.
• Draftback and Process Feedback — browser extensions that replay a Google Doc's revision history as it was typed. Process Feedback is free. We are naming competitors because they serve this case and we do not.

Do this before anything else: revision history is tied to the document in your account, so preserve it — do not delete the document, and do not "clean up" by copying the text into a fresh file.

If you wrote it in Word and it still shows no history

A few ordinary things strip the record: converting through PDF and back, opening and re-saving in an online editor or a converter, or a document assembled by a template or generator. Check whether you have an earlier copy — an email attachment, a cloud backup, a version you sent a supervisor. An older copy often carries the history the current one lost.