The most common cause of not properly loading OptimizePress 3 Builder is an outdated PHP version. We recommend that you run your site on PHP 7, released in 2015 and touted as being the best PHP version to date.
Log in to your cPanel and then upgrade your PHP version from there. If you are not sure where to update your PHP version, please reach out to your hosting support and ask them to update your PHP version to 7.0 for you.
To ensure maximum compatibility, please check out our minimum requirements here: