Roon app can't find my Zen

I have just had my Innuos Zen music streamer returned from Innuos with the latest software update. They told me I could control the Zen with Roon. I have the Roon app on my iPhone and iPad and also on my iMac… When I ask Roon to find the Zen it can’t find it. I believe it is to do with the Roon core but don’t know how to sort it.

My setup:- iMac into Auralic dac - into Bryston headamp/Audeze LCD2 headphones.

Roon 1.5, build 363, 64 bit

I have the Zen connected to my Synology NAS. (24,500 tracks)

My iMac finds the Zen through the network. I can store music files on the Zen which I am told will give me better sound quality than the NAS.

My iMac is listed as the Roon Core and my iPhone Roon app can control the music played.

How do I get the Roon app on my iPhone or iPad to recognise the Zen and play the music stored on it, please?