I noticed this issue on 3/242022 at 7:00pm PST. The YouTube music app throws an error when trying to cast to Chromecast. I CAN cast from YouTube so Chromecast is working. I tried clearing YT Music app data and cache, uninstall/reinstall the app, reset Chromecast and reboot phone (pixel 5) all to no avail. I have called TY Music tech support and they transferred me to Chromecast but I believe this to be a YT Music app issue, at least on Android.