If you added var p = GetPlayer(); in your user.js file, for example, it used to grab the player fine.
In Storyline 360, you're might be getting an error. The problem is that the file itself, user.js is loaded and executed earlier than GetPlayer() is available. (Granted, this method is not supported. If you add JS within Storyline, those calls will work.) As a workaround, you may have to use jQuery document ready to wait for page load, or add a silly SetTimeout function to start executing the the code with a couple of seconds delay (really unreliable way of handling but works).
Anyone having similar issues with solutions previously working?