Thanks for reaching out and I'm sorry to hear that you're having an issue setting up your Chromecast with Google TV. Let's sort this out.
A few questions: what type of Chromecast with Google TV do you have, is it the 4K or HD? Are you using a personal Gmail account or a Workspace account? What's the make and model of the device you're using to set up your Chromecast with Google TV? Have you tried setting it up using the Chromecast Voice Remote?
I'll look forward to your response.