Thanks for posting here in the Google Nest Community.
A few things: Do you have a Chromecast device plugged into your TV or it has a built-in Chromecast? If it's a Chromecast device, which model is it? Are you trying to cast from your phone to your TV?
You can cast from any Chromecast-enabled apps to your TV if it has a Chromecast or a Built-in Chromecast. Check the steps below.
Looking forward to your response.