If I’m understanding your post correctly, you are updating a file via FTP but the corresponding file is not updated when you view the site via a web browser.
First things to always try are refreshing the server page in the browser (typically shift F5). This causes the browser to ignore cached content.
If that’s not the problem, then likely you are uploading the file to the incorrect directory. Start at the steamboat panel, “Manage Domains” page. Find the listing for your domain then look in the “web hosting” column. It should say “fully hosted” and list a user. The user listed here is the user you MUST be using when logging in via FTP. Once logged in you should see a directory with the same name as your domain. The contents of this directory corresponds to the top level of your domain.
Most people reporting your problem have the “user” wrong.