Thread:Project:Support desk/Page reverts to index instead of showing special function such as :Special:Version or MediaWiki:Common.css/reply

It seems like you have a problem with your short URLs. When I use the long form, I can access the pages.

To fix this you will have to fiddle with $wgScript, $wgScriptPath and $wgArticlePath; see the page "short URLs" for details.

Part of your problem might be that you have installed the wiki directly in the webroot. That is not recommended. Instead you should move it into a subfolder, e.g. in a folder called "wiki" or just "w". $wgScriptPath must then be set to this relative path.