Thanks for reaching out and I'm sorry to hear that you're having an issue with your Chromecast with Google TV.
When did the issue start? What type of Chromecast with Google TV device do you have, is it the 4K or HD model? Please try the steps below:
Let me know how it goes.
the official line is the usual "restart your device ad absurdum" until they fix the android 12 release, assuming there is anyone left in the chromecast team
alternatively return the device; people are moving to roku/apple tv/shield instead.