A user is trying to install an app's new features through the website of the developer other than from the Google Play app store where he downloaded the app. What are the TWO possible reasons why the new feature update fails to install?

For apps from the Google Play app store, any updates won't be installed unless the developers' signatures for the update and the original software match. This is a security feature for Android devices. An error message like "Signatures do not match previously installed version" will show up if the signatures don't match. If you downloaded the update from somewhere other than the Google Play store and received this error, there is a significant likelihood that the website is a spoof of the actual developer's site, and someone is trying to trick you into installing malware. Before August 2021, Android apps on the Google Play store were in the Android package (APK) source format. Updates for existing apps might still be available in this format, but any newly created apps published on the Google Play store after August 2021 will be in the Android App Bundle (AAB) format.