Thanks again Urquhart1244. Very helpful.
Q 1) Did you press the Bluetooth button on top of the controller, with the bluetooth screen active on Apple TV, to make it connectable/discoverable?
A 1) Yes, tried Bluetooth buttons in both controllers with the Bluetooth screen active, but neither controller was ‘discovered’ by the search. I selected to forget the first controller, and start again, but the search didn’t discover either controller afterwards.
Q 2) Did you try if a software update for the controller is available, through a computer?
A 2) Yes, I downloaded the Steelseries ‘Engine’, into my MacBook Air, connected the second controller, but I couldn’t find the option to download the latest firmware. I will have another try.
Q 3) Connect the second, in-game, through the first. It may depend on the particular game title: Turn-based games may not aways have support for two controllers.
A 3) Yes, tried this, but I had already selected the first controller to be forgotten, so couldn’t even use the first controller, and in game neither controllers were recognised. I then factory reset the Apple TV and updated it to latest firmware, and tried to pair again using Bluetooth buttons on both controllers, but neither were found on the Apple TV Bluetooth search screen.
Q 4) You could try finding a means to contact an actual SteelSeries Support person (through My Tickets perhaps, where you can sign in).
A 4) Yes, thanks will try this next.
Many thanks again