Thanks for posting. Could you please tell us more about your concern so we can further assist you? Are you unable to cast videos from YouTube to your TV? Is this only happening with the YouTube app or across all apps? Please try to uninstall and reinstall the YouTube app and reboot your Chromecast. Rebooting your mobile phone and using a different mobile device might also help.
Just checking in to make sure that you've seen our response. Please let us know if you have other questions or concerns as we will be locking this in 24 hours if we won't hear back from you again. Feel free to start a new thread and we'll be happy to help.
Thanks for the help, Jeran.