This is indeed a very clear description of how to create a table of contents. It's the way I did it for my novel and it worked fine internally. But it failed to generate the NCX "Go To" table of contents that pops up to the side. I was told by KDP to change from bookmark anchors to "Heading" anchors (using a Heading style for all my chapter and section heads, then linking to them). That didn't work, either! I'm currently in no-man's-land, with a book that displays beautifully in every other respect but that I don't want to release because I know readers enjoy and depend on that secondary, Kindle-generated ToC.
When you create a TOC, all you are doing is creating and inserting a bookmark in every chapter or main section heading in your doc. Then, from your new TOC page you write a list of those chapters or main sections and manually create links to their individual bookmark locations in the doc.
Here's how to manually create a doc TOC in Word.
1. First create a blank TOC page. Add the TOC heading then list all the sections/chapters that you want to see in your doc TOC.
2. Next, for each highlighted chapter or section heading throughout your doc, use Insert > Bookmark to insert a unique bookmark name e.g. title, intro, chap1, chap2, chap3...epilogue, about etc. Do this for all the chapters/sections that you want to see in your doc TOC
3. Now return to your TOC page and link each chapter or section heading in the page's TOC list to its own unique bookmark name or id. You do this by highlighting a chapter/section heading and clicking on Insert > Hyperlink > Place in Document > Bookmarks and selecting the relevant bookmark for each chapter or main section from the bookmark list(that you created earlier). Do this for all your bookmarked headings
4. After doing the above you should now have a fully working doc TOC with links.
To finish off your TOC page properly in Word, you should also insert a bookmark in your TOC heading and name it "toc". Doing this will ensure that your Go To menu on the Kindle device has a working link to your new doc TOC.
I've done all that -- in fact, I did it with the bookmark method and then the KDP helpers said to change the bookmarks to Heading styles, which I did and it didn't help. On my most recent update I added the toc bookmark and we'll see how it goes...IF I can get Amazon to send me a copy of my own book to preview! But that's a whole other issue.
You can't download a preview of a book submitted via Kindle Create. Amazon do not give a reason for this, as far as I know. It is just the way it is. Instead, you download the Kindle Previewer to your computer and open your .kpf file with that. It should show you how your book will appear and work on a Kindle, a smartphone and a tablet. You only need to download it once, so that you can use it with all your books. In my experience, it can be trusted.
When I first used KC, I didn't put in a ToC, but the Previewer still flipped from chapter to chapter when told to do so. Then, as I grew a little more adept, I created my own ToC, using the prescribed method, and everything works as it should.
Analyse exactly what you did to check whether there is an inadvertent error in there somewhere. It's a long shot, but is it possible that your file has become slightly corrupted somewhere along the line, and this is manifesting itself as the ToC problems? These things happen. The way to check it is to save it as Plain Text. This will strip out all your formatting, save the carriage returns, leaving you with just the words. You will then have to put the formatting back in again, of course. I recommend marking each instance of italics etc. with a character you don't normally use so that you can find them again easily. The stripping out of the formatting will also strip out whatever corrupted the file, leaving it corruption-free. Like I said, though, it's a long shot. It might be worth a try, though, if all else fails.