You must set the top-level domain for your Snap-ins Chat deployment in your upgraded code snippet. For example, if you set MyAwesomeWebsite.com for your top-level domain, your chat visitors can navigate to subdomains like help.MyAwesomeWebsite.com while they chat.
Add the following to your snippet to set your domain (but replace MyAwesomeWebsite with your domain, of course!).
embedded_svc.settings.storageDomain = 'MyAwesomeWebsite.com';