As you may have noticed, a new version is rolling out at the moment, with a lot improvements and new features (including a "report cheater" function, as promised!)
Unfortunately, we had to remove the Chromecast function from the game. The reason behind that is not that we don't want you to play on big screens - it's more complicated.
Google decided to drop the support for the Unity plugin that was developed with us and custom-tailored for running RISK via Chromecast.
Therefore, as we are forced to update our technology and plugins constantly in order to bring you new features and supporting new devices, we had to let go of Chromecast for now.
Best of luck in your future RISK games!