“Word experienced an error trying to open the file” is not one problem. It is a symptom with a short list of causes, and the cause decides which recovery method works. The good news: for .docx, the text almost always survives. The structure around it is what breaks. ...
If Word crashed, was force-quit, or the machine rebooted with a document open, the text is often still on disk. Word writes copies to three different places, and which one has your content depends on how far the crash was from your last save. Search them in this order. Do it before reopening Word, because opening a new document can overwrite the most useful folder. ...