Why can't I get some jpg photos to show as thumbnails on this windows 10 pc? Some show, some don't. The ones not showing are on the desktop in folders and also elsewhere in folders on C drive. It's not only one folder or file location having the problem. There are a lot of photos on this PC in a lot of locations.

I tried:

 

1. Windows is up to date.
2. There is lots of room on C drive still.
3. Checked file explorer options

File Explorer Options > View tab ... no check mark on 'always show icons, never thumbnails'

 

1. Tried Setting the File Explorer Options to Default: in view tab, clicked Restore Defaults
2. Checked Visual Effect Settings-Show thumbnails instead of icons options is checked (Save taskbar thumbnail previews is not) not sure if 'let windows choose' radio button was on. I think it wasn’t. Think it was on 'custom'
3. Used windows Disk Cleanup to delete thumbnail cache on C drive by deleting thumbnails only
4. Ran sfc /scannow
5. Checked to make sure the non thumbnailed files had the jpeg extension name by unhiding the file types
6. Temporarily turned off the antivirus (forget what kind of AV it was)
7. Tried changing which program opened the file type (presently left it on the photos app which is what it was on before)
8. Tried renaming a photo file missing its thumbnail, didn’t accomplish anything
9.  

Further info and observations:

There are a fair number of folders on the Desktop containing lots of files, mostly photos. Could this be causing the problem? I'm old school so storing files on the desktop has always been a 'no no'. I didn’t try moving the file folders to another location like 'photos' because the PCs owner wasn’t present to ask permission.

Most but not all photos have the OneDrive two blue static arrows showing but OneDrive is not signed in. Couldn't login to OneDrive without PC owner present.

Copying and pasting a folder where some or all pictures are missing thumbnails to another location (ie from Desktop to 'my documents') causes the thumbnails in the new location to appear. If you then put the copied folder back on the desktop, the thumbnails still show as they should.

When viewing any folder using the photos app (opening the app and browsing photos in folders from within it) the app itself shows the photos no problem. It also appears that after viewing a photo within the photos app the thumbnail re-appears on the photo in the folders. (Just opening the photo with the photo app doesn’t 'fix' the thumbnail)

Has anyone got a suggestion what to try next to get all the thumbnails on the photos to appear?