Assuming the iPad is compatible, and you only have supported speakers in your Sonos ‘room’, it should be working. 

It won’t work, I think, for instance, if you’re using a beta OS from Apple. 

I’d probably call Sonos Support to discuss it.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Many thanks, will ring them,  it’s an iPad 13 with the latest update 

I don’t see the iPad 13 listed on the linked FAQ as supported, I’m guessing that’s your issue. 
 

Neither of my iPads are supported, but my iPhone is, so I use that, on the super rare occasions I need to do a TruePlay session. Frankly, for most rooms, I skip it, I find it to be only mildly helpful in some rooms, not at all in others. If I felt it was much more than a marketing ‘gimmick’, I’d suspect Sonos would make more effort into making it available for Android. Useful for poor speaker placement, nut there are limits as to what can be modified, I suspect. Certainly not required, IMHO.

Thanks for your response, I will try my phone,  any reason why the latest iPad is not compatible, seems they have intentionally not made it compatible for some reason 

I don’t work for Sonos, so any conjectures I have are just that. I suspect that the amount of effort needed to verify each device is large, and the number of people capable of doing the work are few, or tasked with other perceived issues. I don’t think there is any ‘intentionality’ involved, just effort not yet made, or possibly changes made by Apple that makes it harder to ‘verify’. 

I don’t think Sonos has ever had infinite resources to apply to each issue concurrently, I suspect there is a certain amount of choosing / prioritizing done.