If you are in the United States, you may want to update your WWE app. Today, they announced support for Google Chromecast. There seem to be some bugs right now so you may have trouble casting to your device. If you are having trouble casting from your device then try power cycling your Chromecast. Basically, power it off (unplug it) for 10-20 seconds and plug it back in. Let Chromecast restart and then try casting again from the WWE app. If you are still having issues then try deleting and reinstalling the WWE app.
The Chromecast support for the network has been something that fans have been waiting for since they launched three years ago. Last June, WWE.com’s network updates page promised Chromecast support but it took many months to roll it out.