UE4 why is audio (attenuation) coming through both ears equally when to the right of player on mobile?

I have a mono audio that has attenuation turned on.

On PC, when I turn so that the audio is to my right, the sound only (for the most part) comes through my right ear. However, on mobile (Android), the audio comes through both ears equally. Why is this?

The player is unable to tell where the enemy is in my game because he cannot tell where the sound is coming from.

Thanks!