Thanks for reaching out and I'm sorry for the late response. Let's sort this out.
A few questions: is this an initial set up or working previously? What type of Chromecast device do you have? How far is your Chromecast from the Wi-Fi router and set up device? Are you using a dual band router?
Give these steps a try:
This is an initial set up of a Chromecast with Google TV. Running Google wifi mesh system throughout the house. Set up device is iPhone - so standing right next to it. Yes running Google dual band router. Part of the problem is the Chromecast doesn’t get past the multi-colored G on the TV screen - and the device doesn’t show up on the Google Home app set up process. Light on device stays white - even when attempting hard reset via button on back.