Why it failed to generate a thumbnail image of the file?

DiskCatalogMaker will use QuickLook to generate thumbnail images.

DiskCatalogMaker cannot generate a thumbnail image from a file which Finder cannot show its QuickLook preview. (Finder also uses QuickLook to generate a thumbnail image.)

FYI: Some legacy .mov formats are no longer supported by QuickLook of Mac OS X 10.9 or later. (Apple Communities: Quicklook no longer previewing Quicktime videos encoded in ProRes or Animation codec.)

See also: