Native method GET_SOUND_ID returning null

I'm working on a small helper method for my RagePluginHook plugin, this is what I've got so far:

public static int PlaySoundAtLocation(Vector3 position, string soundName, string soundSet, bool loop = false)
{
	int soundId = NativeFunction.Natives.GET_SOUND_ID(); // Crashing on this line

	NativeFunction.Natives.PLAY_SOUND_FROM_COORD(soundId, soundName, position.X, position.Y, position.Z, soundSet, false, 0, false);
            
	if (loop)
	{
		NativeFunction.Natives.SET_VARIABLE_ON_SOUND(soundId, "Looped", true);
    }

	soundIds.Add(soundId);
	return soundId;
}

When I try to call the GET_SOUND_ID native, I get this error message:

RuntimeBinderException: Cannot convert null to 'int' because it is a non-nullable value type

Does anyone know why GET_SOUND_ID might be returning null? Is there some form of initialization it requires?

Thanks!