This is just an informational post to save anyone else hell who may come across this issue setting up a Chromecast Audio that has never been updated before.

It will be on an ancient firmware and will fight you every step of the way -- your phone(s)/Chromebooks may connect to the device itself, but it will fail and fail connecting to a wifi network. If you're stuck where setup continuously says "check password" despite it being 100% right, or "might not be configured to connect to / communicate with other devices", this info is for you.

1) Use an iPhone for setup with the Google Home app. Seriously. I tried for hours using my Pixel 6 Pro and a Chromebook, and the Google Home app wouldn't work, and the Device Utility app wouldn't work either, to get it connected to wifi. The iPhone (11 Pro Max in this case) was part of the solution.

2) Set your wifi router temporarily to the 2.4gHz band ONLY (no mixed channel APs). The older firmware will refuse to connect to 5gHz.

3) Set your wifi router to unsecured/no password. This is critical if it won't connect after you set it to 2.4gHz. Reconnect your iPhone to this unsecured network.

4) Then, go on the iPhone to your Google Home app to set up the new Chromecast Audio, and it will work. If it doesn't, factory reset (press and hold button on side til it turns white) and try again. It will work.

5) The firmware for the Chromecast Audio will update for 3-5 minutes, just let it do its thing.

6) Once the device is complete with the firmware update and you have verified you can see it online and in your Google Home app on the iPhone, go ahead and set your router back to your security level of choice with a password. You should also set your router's access point back to mixed-band (2.4gHz 5gHz) if you had it enabled previously.

7) Reconnect your iPhone to the wifi now with your password.

8) Press and hold the side button on the Chromecast Audio until the light turns white. This will factory reset it so you can set it up to connect with the router's updated configuration.

9) Open the Google Home app and take the Chromecast Audio through setup one more time, input your wifi password, and it will connect. All is well.

I hope this helps someone out there! It was impossible for me to find this info online so I troubleshooted all day until I forced it to work.