Responsive Scroll Triggered Box is using Mobile Detect, a lightweight PHP class for detecting mobile devices (including tablets). It uses the User-Agent string combined with specific HTTP headers to detect the mobile environment.
In order to avoid conflicts and PHP errors, It loads the Mobile Detect Class ONLY if it's not already loaded by another component/plugin/template. However, there are many Joomla extensions out there which don't make this check as a result the following PHP fatal error.
Fatal error: Cannot redeclare class Mobile_Detect in /home/../Mobile_Detect.php on line X
Go to Joomla Plugins Manager and find the Responsive Scroll Triggered Box - Render plugin. Then try to re-order it at the end.
If the problem persists please contact the extension's support team and ask them to fix the error.