You may need to use FN + Display on the remote to get the speakers to go through the displays... If not, put the system into standby and press CLEAR on the remote to make sure there is only one controller.

As Bruce said, I would have expected the speakers to use SpeakerLink (which is the same as a Network Cat-5 cable) as that will give a better sound (using a balanced digital connection).
It also allows the 818v3 to better communicate with the speakers (i.e. when you change settings on the 818, it can update the speakers).

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200.2HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5200HC, DSP33
Spare: MCD, 100 Series, 200 Series, 500 Series, F80s, C15s.