WallpaperManager crash in Unity Android Live Wallpaper

Question

I'm trying to build a live wallpaper by linking Unity to Android. I keep getting this error which happens inside the android code WallpaperManager. Anyone has any clue what is going on?

I'm using Unity 2019.2.21f1 and compile using a Unity tool from Asset Store link

Caused by java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.WallpaperManager.notifyPid(boolean, int, java.lang.String)' on a null object reference
       at android.service.wallpaper.WallpaperService$Engine.attach(WallpaperService.java:1326)
       at android.service.wallpaper.WallpaperService$IWallpaperEngineWrapper.executeMessage(WallpaperService.java:1732)
       at com.android.internal.os.HandlerCaller$MyHandler.handleMessage(HandlerCaller.java:44)
       at android.os.Handler.dispatchMessage(Handler.java:107)
       at android.os.Looper.loop(Looper.java:237)
       at android.app.ActivityThread.main(ActivityThread.java:8019)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)