Gateway Timeout is an error returned by a proxy between you and the Autoslash site itself. It is not a problem with the site but rather an intervening server, most likely one that your company maintains. They may be blocking or disallowing access knowingly or unknowingly, with or without a reason.

Another browser on the same PC is not likely to effect the situation; trying from a different location (like home) is basically your only recourse short of taking it up with your company's IT dept.