Sorry, I was confused by your wording. Makes sense.I asked if his iPhone and remote app were up-to-date as this may have caused an issue to him not using the remote app via ATV 4.
I'm currently still at work so I can play around with my new ATV 4 yet. The only thing I could think of is that there is a new update for remote app, that needs to be done and hasn't been released yet.