We’ll assume, for the sake of the tutorial, that you are able to access the previous Wi-Fi network as well as the new one. If you’re unable to connect to the old one, you’ll need to do a factory reset. Than again select the network form the list. 
Although while selecting Network keep one thing in mind that Chromecasts can only connect to 2.4G networks. Devices that can connect to 5GHz networks or Ethernet will be able to connect to Chromecast provided they are on the same router.
- Open the Chromecast app on your Android or iOS device
- Search and connect to the Chromecast
- Open the settings page
- Tap the Wi-Fi network
- Select the new network from the dropdown menu
- Enter network password
- Save
Note that you will find a message advising that your mobile device and Chromecast will not be on the same network. Simply connect your device to the proper network and you’ll be in business.
Ibought Chromecast and set it up with my Samsung Galaxy III so I could receive the MLB games. I set it up fine and watched the first game with no problems. Then my cable went out and I thought it was the Chromecast so I disconnected the Chromecast from my TV. After I found out it was the cable I reconnected the Chromecast but have since been unable to get the games on the TV. I can get them on my phone but not on the TV. It will sometimes say it is casting and it will recognize the name I gave to chromecast but it won’t stream to the TV. I use the HDMI2 input channel. HELP! I called MLB and went through several “exercises” with them and they said the problem was with the chromecast.
I can not get chromecast to cast