Just a Tip if you have this issue as it was very anoying for me until i found out the problem.
The new Version of Photoshop (at least for JPG) seems not compatible with SageThumb 64 bit anymore.
I totally forgotten that i had installed this tool which makes possible to have thumbnails on PSD under Windows.
So if you have the issue that you don't see the Thumbnails of JPGs saved with Photoshop 25.0 and above, make sure to uncheck the .jpg extension in SageThumb. Photoshop can't read the thumbnail generated by SageThumb.
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