I finally fixed it!!
Since OneDrive was mention in other replies and I too use OneDrive, I went into OneDrive and unchecked "Save space and download files as I need them". As soon as I did that (no restart needed), the thumbnails loaded for every image in every folder!!
Can't believe it was that simple, yet the Microsoft Team couldn't/didn't figure it out and post the fix on any of the 50 or so threads with the same problem, and that I've scoured looking for the fix!
SMH . . . Another corporation that our money and support has made too big to be bothered with us.
finally a solution that worked.
I had a onedrive folder on my server with all my pictures. if i viewed the folder on the server it looked fine. if i viewed that folder that is also shared on my network via my laptop it was missing thumbs.
tried this setting on my laptop, no joy. tried it on my server and all the thumbnails populated on my laptop again.
it works :).
thank you.