Hey Evans,
With the latest updates to FIrebase Authentication, the user's sign-in session doesn't expire anymore. We instead have infinite credentials and a short-lived token that automatically refreshes (every hour). This gives your user the best experience, because they won't have to sign-in repeatedly, while keeping your app secure, by having a short-lived access token.
Most of our samples depend on onAuthStateChanged and they've been working without problems. Can you post the minimal code that would allow us to reproduce that problem? Keep in mind that this might be a better fit for Stack Overflow, which we recommend using for code-related questions.
puf