Android Music SDK Authentication always shows Install AppMusic App even though AppMusic App is already installed!

I had this issue as well and just managed to resolve it. You basically need to add the code below in the manifest.

On newer versions, there is a piece of code that looks for this package and it can't find it so with this you'll be able to find it.

What's the solution to this problem?

I had the same issue and was able to resolve it by adding the Apple Music app ID "com.apple.android.music" to the queries element in the manifest file:

<manifest xmlns:android="http://schemas.android.com/apk/res/android" >
    ...
    <queries>
        <package android:name="com.apple.android.music" /
    </queries>
</manifest>

According to the Android documentation, the <queries> element is needed for your Android app to interact with another app (in this case the Apple Music app).