Thread:Project:Support desk/Error creating thumbnail: convert: Unrecognized option (-thumbnail)./reply (2)

You don't have image magick installed, or more likely have another program thats not image magick installed with the name convert.

You need to either set manual:$wgUseImageMagick to false in LocalSettings.php, or install image magick, or fix where mediawiki is looking for image magick (manual:$wgImageMagickConvertCommand).