Hey there LynLee,
I apologize about the late response, thank you for your patience on this! In case you haven't already got that device setup, I'd be happy to help out! The first thing I would recommend you do is factory reset that Chromecast device to clear out the old network information. After that, check out this quick set-up guide to get the device up and running again.
I hope that helps you out, and if you have any other questions or concerns for me, please let me know!
We haven't heard back from LynLee, and it's been a few days, so I'm locking the thread. As always, feel free to make a new thread if you have any more questions or concerns.
Have a good one!