[slowsmile]

@NotJohn...I've used and tested the online Word2CleanHTML app. This app does indeed clean up the HTML but unfortunately it also zaps most of the styling in the HTML. That sounds rather dumb to me because that means that you must re-style your HTML file from scratch in Sigil. So you're actually duplicating your work and creating more unnecessary work for yourself. Is that sensible?

There are much better ways to clean up your html while, at the same time, also preserving all the styling. For instance, as one of its tasks, my OpenDocHTMLImport plugin will first thoroughly clean out and reformat both your html file and CSS file for you and will leave you with a working html file that you wont have to restyle from scratch in Sigil. I use mostly bs4 for cleaning out the proprietary dross from the html file and this works quite well.

I would also second DiapDealer's comment. Sigil's Mend HTML on Open facility is also a very useful way of loading in html files derived from Word(as Web page filtered html), AbiWord, Google and OpenDoc into Sigil. I've also found that, so far, the only html file that it won't load or accept is a Word doc saved as just a Web Page(not filtered html).

From the above, I'm also guessing that the OP probably just saved his Word doc as a 'Web Page' which wont work. But if he had saved his Word doc as 'Web Page Filtered html' and set 'Mend XHTML file on Open' in Sigil Preferences as advised then it would probably load into Sigil without no problems. I've also just followed this procedure using a Word filtered htm file and it loaded into Sigil without any problems at all.