Thanks for posting here in the Google Nest Community.
I know how it feels when something isn’t working as it should, so let’s check what’s going on. A few things: does your TV have a built-in Chromecast or a Chromecast device plugged into it? If there is a Chromecast device, which model is it? When did your issue begin? Were there any recent changes made before the issue started? What steps have you taken so far?
You can do a sequential reboot. First, unplug your TV for 30 seconds, then do the same thing to your Wi-Fi router to refresh both devices and your Wi-Fi signal.
Keep me posted.