MS 365 files (Word, Excel, PPT) no thumbnails in Windows Explorer

I installed MS 365 a few weeks ago and have recently noticed that its files are not showing thumbnails when looking at them in Windows Explorer. All files are saved in the latest format, e.g. docx, xlxx, pptx. This is whether viewed as large, medium or small icons.

For a Word file I see a default icon with W middle left. For Excel a default icon with X middle left.

File & folder options:
Always show icons, never thumbnails - unticked
Display file icon on thumbnail - ticked

pdf, jpg, png, files are fine, it's only the MS 365 files that are odd. Even then some of the Excel files will show a thumbnail and the very occasional Word file.

Files are saved in the latest format (as far as I'm aware), with Save Thumbnail ticked. For Word files Maintain compatibility with previous versions of Word is unticked.

I've tried changing the Files & Folder settings for all folders. No difference. Tried clearing the thumbnail cache, no difference except lost most of the thumbnails for files that previously showed thumbnails.

I thought it might be to do with settings of particular folders as it seemed that, occasionally, copying a file from a folder where it didn't show a thumbnail to another folder resulted in the thumbnail being displayed. But that wasn't consistently repeatable and isn't happening now anyway.

Are there any other things I can try?

Edit: I see that you already save with the option to save a thumbnail enabled. I never noticed any difference with that option selected. What is actually supposed to look like? Should it actually look like a thumbnail of the actual document?

Okay, just stumbled upon something by accident. In the toolbar for Word, my Microsoft account name is displayed. I clicked it and it said it could not access my account. There was a logon option. I logged on and then when I saved to doc the thumbnail worked.

For another existing file I had to save it to a new filename and again the thumbnail now shows up.

Don't know if this will help you, but thought it might be worth noting.

I've checked the account, it's logged in and always has been as far as I know

The following are all with Save thumbnail checked.

I've just tried saving an existing Word document with a new file name. No thumbnail.
Created a new Word document. No thumbnail.

A very small number of existing Word documents are showing a thumbnail. Some have been recently saved. But other recently saved Word documents don't show a thumbnail.

In one folder I have mainly .doc files, a few are showing thumbnails, many are not.

As for Excel that seems random as well. Some show thumbnails, some not.

.pdf, .jpg, .ico and other file formats seem to show thumbnails ok.

It seems to be an Office / File Explorer issue, but goodness knows what.

Indeed. Checked and double checked. Also looked at the setting for some Word files that displayed a thumbnail and some that don't. They both have it checked.

As Alice said in Alice in Wonderland "Curiouser and curiouser!"

Thanks. Yes, I've tried them all

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Just looked on my laptop, running the same Windows 10 version, running the same MS365 version, and Windows Explorer shows the thumbnails for files that, when on my desktop, do not show thumbnails!

Can't see any difference in folder settings. When time permits I'll try to put them side by side and compare everything.

Definitely an odd one.

Have you figured out what the deal is? I just did a fresh install of Windows 10 Professional on a brand new SSD and now all of the Office files will not show thumbnails nor do .txt files. All graphic files and PDFs are showing thumbnails properly. Seems to only be Office. This is rather annoying...