This is what I see when starting my game from the APK file. I've tried a number of things. Mainly these fall into the category of building with or without Gradle and building for different SDK versions. I've tried 34, 33 (seems to be the default) and 32. My phone is using Android version 13 which I believe corresponds to SDK 33 (according to Android Studio at least). The phone is a Samsung Galaxy A71 5G. It's maybe 18 months old. I'm developing and building my export files on Ubuntu Linux 22.04. I've googled this error message but the only links to it seem to be ones like this - https://ask.godotengine.org/33797/cannot-install-apk-on-android. That site appears to be down though and has been for at least the last few days. Does anyone have any ideas about what's happening?

Oh, and the game DOES run in the Godot editor. I've tried versions 4.0.2 and 4.0.3 with the same results.

    The best thing to do is to start with the basics and make sure your APK is correctly configured and signed. Since your error message indicates that the "APK signature verification failed", this implies that the APK was not correctly signed. Try following along with the steps outlined in the How to Sign Your Android APKs guide.

    Also, are you using ProGuard for code obfuscation when building the APK? If so, ensure that the relevant configuration files are correctly set up. Similarly, if you're using any third-party libraries, verify that all of these dependencies are correctly set in the Gradle build configs.

    If the compliance issue is not related to incorrect signing or dependencies, it's a good idea to debug the Android device logs to see what’s going on. You can do this either with a USB cable and the Logcat tab of the Android Device Monitor in Android Studio, or by using the Android Debug Bridge (ADB), which can be accessed from the command line.

    In addition, make sure you're using the right Android SDK for the phone you're trying to run your game on. If the SDK version of your game is lower than the phone's Android version, it might also lead to compatibility issues.

    If you're still having issues, try posting your APK on the Godot forums and include as much information as possible (such as the relevant code and any build logs) so that other developers can try to reproduce your issue.

    gpropf I feel a little embarrassed here. It turns out I didn't have a main scene defined so the game didn't know where to start. Problem solved!