Hi.  You have disabled all wireless capability on the Arc when you 'disabled WiFi', making it impossible for the Arc to communicate with the Amp in the way required.

The Arc communicates with the Amp using direct routing over 5GHz. 

If you wire the Amp as well then it will probably work, but not as designed. 

Thank you for your response.

I have to admit I’m a little am disappointed.  What is the point of offering to disable wireless if it makes the unit unable to communicate with other devices?

What about if all 3 units are wired?  The Arc, the Amp, and the Sub.

Not sure why you are disappointed. 

The option is designed for fully wired installations. So yes, it should be OK if you wire everything.

I guess I’m disappointed that a mixed wired/wireless setup isn’t an option.  I did a fair amount of Googling, and found no such caveat to such a deployment.  Perhaps more obviously, when you disable WiFi, the system should warn you “disabling wireless on a single system does not work.  You must disable at the Room-level or higher.”

For an otherwise user-friendly, novice-friendly system, this is a glaring gap that could easily be detected, prevented, or made obvious to any user.

Many folks here have been telling Sonos over and over that a simple change to the menu wording there from WiFi to Radio would end much of the confusion.