New roam grouping problem.

Hi

I have two sonos one sl speakers. I use them from my iPad & they stream Tidal successfully. 
 

I’ve just bought two roam sl & also play them through my iPad. 
 

however, the four speakers don’t appear on my app. I have to switch off one pair to use the other; hope that makes sense. 
 

what have I done wrong? 
 

how do I group them together using Tidal?

Thanks for any help. 
 

Sim.