Waking up ps4 from iPad

[Aethelstan]

I listen to Spotify on my audio system via the PS4 app, and control what's playing using my iPod touch.

the Touch can also wake up the PS4 using Spotify connect - when the ps4 is in standby I simply open Spotify connect in the iPod app and tap the ls4 icon, which wakes it up and activates Spotify.

I also use Spotify on an iPad Air 2 occasionally, but when the ps4 is in standby mode and I open Spotify on the iPad, the ps4 icon in Spotify connect is greyed out and I can't wake it up.

Is there something I'm missing that I need to do to be able to wake up the PS4 from my iPad as well as from the iPod Touch?