Rebuilding Thumbnail not working in Xn View Software

[bsac]

I have a bunch of photos that are missing thumbnails.

When I go to the menu item Metadata using XnView software the EXIF- Thumbnail > Rebuild is greyed out and not working.

Please advise on how I can add thumbnail images to my photos.

Best, bob

[xnview]

it's only to rebuild embedded thumbnail for jpeg files

[bsac]

huh?