Dear kathy61,
we were supporting auto-filleven for Samsung Internet Browser, but then Samsung release a new version of mobile browser and unfortunately our auto-fill feature won’t work with this new version right now.
Browsers which we support on mobile platforms are Mobile Google Chrome & Mobile Opera browser. . If you have auto-fill turned on (you can check it in the settings in Android Avast Passwords app), you should see the overlay icon in these support browsers.
May I ask if you see a "failed to open settings for Avast Autofill” message while using the Internet Browser casually, or only if you click on "Avast Autofill" in Settings/Language?