I apologize about the late response, thank you for being patient! Were you able to fix that connection issue? If not, I'd be happy to help out, as I know networking problems can get confusing. If you haven't tried already, I would recommend that you factory reset the Chromecast to forget the old network. You also marked that you have a 1st generation Chromecast, so make sure that your Wi-Fi network is a 2.4GHz band, as those older models cannot connect to a 5Ghz band.
I look forward to your response, and if you have any other questions or concerns for me, please let me know!
Hi Jillleah and Dbpactman,
Just checking in to make sure that you've seen our response. Please let us know if you have other questions or concerns as we will be locking this in 24 hours if we won't hear back from you again. Feel free to start a new thread and we'll be happy to help.