Looks like you can't create a guest network with the XB7 gateway so you'll have to turn off WPS on your main home network.
From Google AI:
To turn off WPS on an XB7 router, access the admin panel via a web browser, navigate to the Wi-Fi settings, and locate the WPS option. You can typically disable WPS by clicking a button or checkbox associated with WPS settings.
Detailed Steps:
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Access the Router's Admin Panel: Open a web browser and type the router's IP address (usually 10.0.0.1) into the address bar.Log in: Enter the username and password (often found on a sticker on the router).Navigate to Wi-Fi Settings: Look for a "Wi-Fi," "Wireless," or "Network" section in the admin panel.Find WPS Settings: Within the Wi-Fi settings, locate the WPS or Wi-Fi Protected Setup options.Disable WPS: You should find a button or checkbox to disable WPS. Click on the button or deselect the checkbox to turn WPS off.Save Changes: Save the changes in the admin panel.
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Note: Some routers might have a WPS button on the front or back of the router. Pressing and holding this button for a specified duration (e.g., one minute) can initiate a factory reset, which may also disable WPS.