I received an error similar to Fatal error: Uncaught PDOException: SQLSTATE[HY000] [2002] No connection could be made because the target machine actively refused it. How do I fix it?

The premium version of the plugin uses a PHP Module called PDO to handle the database functionality for xAPI support.  This is typically installed by default.  Your hosting provider should be able to resolve this for you per:

https://stackoverflow.com/a/2852997