Microsoft Word is reopening documents that I've already closed when I respond "SAVE" to a dialog box. But MY WORK IS NOT SAVED.

Using Microsoft Word's most recent update (Nov 2023) on a MacBook Air using OS Sonoma 14.1...

I can manually save changes in my Word document and the changes appear to be saved. The problem only occurs when I try to CLOSE the document. Then -- even though I've already saved my changes -- a dialog box appears saying I need to save my changes or lose them. The other options are "Don't Save" or "Cancel". So, I press "SAVE" and the document appears to close BUT IT REOPENS. Every time I retry the sequence I get the same result. I cannot close the document. And if I were to press "DONT SAVE" (just to be able to close the document), then none of my changes are saved, even though they appear to have been saved while I was editing it.