Hi Bryan, each case above is different - this isn't the same problem for everyone. There are many things that may affect whether your site is editable in SimpleCMS so it requires a bit of investigation on our part if you are having problems.
I have checked your FTP details and they are working but I'm not sure that they are linked to the site you have added to your account. I downloaded /httpdocs/index.html and added a comment tag <!-- test --> to the top of the file. When I refreshed your site's URL and viewed the HTML source the comment tag wasn't there.
I have also uploaded a new page "testing.html" and tried to view that on your site but it was displaying a 404.
Could you double check / update your FTP settings.