I found the cause of the problem.

While adding the mp3 files I also added code to use the mp3's.

val soundEntry: Int = soundpool.load(context, R.raw.mp3file, 1)

That made the Android Studio to auto import android.R

I though of removing the question as this was my error, but decided to leave it for other naive programmers like me that will experience this error and not lost there mind.