NEBULA PRIZM II Not connecting to iPhone

Hi all

I have a Nebula Prizm ii and I’m having trouble connecting to my iPhone. I have an iPhone 7.

It connects in so far as it recognises that the iPhone is there, but when I select any apps (including free) it doesn’t play through the projector - just a black screen. Even for apps that I have subscriptions for - ie ITV Hub.

These all work on my partner’s iPhone (8 plus).

Is there a setting somewhere in my phone that I need to change to allow the connection to take place?