Problem Files

[Darius1968]

Attached are two jpeg files, for whom IMatch isn't generating thumbnails, despite the fact that the File Explorer in Windows 10 does oblige this requirement.  So, what could be wrong with the files? 

[Mario]

These images are not JPEG files but files in the obscure Google WEBP format.
If you change the extension to the correct .webp and then force IMatch to rescan the files, it will work.

[Darius1968]

Very interesting! 
And, so, I used the ExifTool Command Processor to list the metadata, and it did enumerate that WEBP format.  But, why does the Metadata Browser not identify the correct image format? 

[Mario]

But, why does the Metadata Browser not identify the correct image format?

IMatch does not import on-the-fly metadata in the [File] section produced by ExifTool. This data is redundant and never needed. IMatch does not care for mime types encoded as text in files (Google is the only one who uses this, anyway). Just make sure that your files have a proper file extension and don't store WEBP files with a JPEG extension and all will be well.