Last year I researched that the Sonos One SL speaker was compatible with the S1 app - and requested one for Xmas so we could use it as an extension to our existing system. 

By the time I received the speaker & tried to set it up, it seems this situation has changed, and I have been unable to get it to work on our existing system. I have had to create a new registration and set it up on a the S2 app just to be able to get it to play. However, this means I am unable to play the same music on the One SL as the rest of the house, which is pretty annoying because this was the reason for purchasing it.

Is there really no way to connect this to our old system? At first, I assumed I just needed to use the Downgrade option - but that would not work either.