Thread:Project:Support desk/MW 1.23.3 - "404 Not Found" then I try open uploaded images or generate thumbnails/reply (3)

Apparently it's a misconfiguration of your webserver.

This URL works: http://echoespro.creativereactor.ru/index.php?title=File:CombineLogo.png

Every URL where you use short URL syntax (index.php/pagename) ends in a 404 error if it ends with a known file extension (.png, .jpg, .txt... but not .mng for example).

It may be some rewrite rule on the server, or something similar.

Look at the error logs of your server to see more information.

Alternatively, disable short URLs by setting $wgUsePathInfo to false.