CMS Made Simple Forums

My guess would be that it's a very old version of CMSMS, and now that most browsers don't allow mixed content (http & https) it's not loading the stylesheets and/or scripts. There's a few ways around this to get you to a point where you can upgrade, but they can be a bit complex so we'd want to make sure that's the issue first. Can you share your CMSMS version and your PHP version?