@abboota
You may need to contact Support for assistance. Google Nest does not make it easy to change Wi-Fi settings on its devices.
Google Nest provides these instructions when you're changing the Wi-Fi network of a Google Nest speaker; they need to be performed while your Nest Hub Max is still online (on your old Wi-Fi network):
"If your speaker or display is already set up on a Wi-Fi network but you need to change your Wi-Fi password or connect it to a new network, you'll need to forget your current Wi-Fi network and set up the device in the Google Home app again.
1. Open the Google Home app.
2. Tap and hold your device's tile.
3. Tap Settings and then Device information.
4. Tap Wi-Fi and then Forget This network.
5. Return to the Google Home app home screen and follow the setup steps above to connect your device to a new Wi-Fi network.
If you get an error message that says "could not communicate with your [device]" when you try to forget your network, or the steps above don't work, you'll need to factory reset your device and set it up again."
https://support.google.com/googlenest/answer/7170507
If you didn't follow these steps or they didn't work, then you need to factory reset your Nest Hub Max by first removing it from the Google Home app while it is still online (on your old Wi-Fi network), and then by pressing and holding both volume buttons together for about 10 seconds until your Nest Hub Max lets you know that it's resetting.
https://support.google.com/googlenest/answer/7073477
If you were unable to do that or it didn't work and you're getting a message saying the Hub is connected to another account (indicating the reset didn't work and the Hub is still connected to your account on your old Wi-Fi network), you could try contacting Support, using the link and instructions in this post:
https://www.googlenestcommunity.com/t5/Cameras-and-Doorbells/Using-Google-Nest-s-quot-Contact-Us-quo...
