using pyChromcast to cast plex

Hi

I am working on a home automation system and I am trying to get it to work with Plex. I am able to use the API to get all the info about the show and even a streaming url but I am unable to cast it using the plex CC app.

the app will launch but it will not play anything. I think there is something wrong with the load command I am using but I am unable to find any doco on it.