I have a house with an excellent wifi system, 8 AMP units hooked to ceiling speakers, and everything plays fine and is reliable.

I am trying to add 2 SL-One speakers.

They won’t join, I go through the procedures but they never show up in the list of rooms after I am done.

I take them to the wifi rack, hard wire them in and they join and work.  Unplug them from the Ethernet wire, and they still play in the system.  Unplug them from power, take them upstairs, and plug them back in and they are gone.