I have gone round in circles and tried all the advice. The only thing which is now suggested is that I perform a factory re set, however I don’t think this will work as I want to connect to a new wi fi . Am I right in thinking this don’t work ?
Thanks for the help here, Ashepherdson.
RayUk, resetting your Chromecast to default settings is the next best step. Give it a try!
Also, you may try to manually connect it to the Chromecast SSID. Here's how: Go to the phone Settings > Open Wi-Fi and connect to the Chromecast SSID (Example: Chromecast1234, Living Room TV, Bedroom TV, etc.) > Go to the Google Home app and try to set up again.
Let us know how it goes.