Sub Gen 3 and Beam Gen 2

Odd. Have you temporarily wired it to your router with an Ethernet cable? Is the WiFi turned off on your Beam, perchance? Have you called Sonos Support directly to discuss it?

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

I am going to contact them tomorrow. I have hooked it to the router directly, also hooked to an Ethernet switch attached to the router with the Beam connected to it as well. The Beam shows up on the app when I have wifi disabled but still unable to add the sub. When I try to add the sub, it starts then says it fails due to connection regardless of being wired or not. 

Odd. Please come back and let us know what support tells you. 

Couple of things I’d try/check, though. First, turn on the WiFi on the Beam, the ‘normal’ connection for the Sub is via a hidden 5Ghz channel between the Beam and the Sub. Worth testing, at least, before turning it back off, just to ensure that isn’t an issue. Second, and perhaps not important if the previous works, make sure your switch isn’t ‘managed’, but an ‘unmanaged’ switch, as the former frequently block settings that Sonos uses. 

I've even gone as far as direct wiring the sub to the Beam through Ethernet. It was worth a shot. My switch is unmanaged as well. Luckily I work in networking so I've gone through a few odds and ends but it just seems like maybe the sub is bricked. I thought about cracking it up open and seeing if maybe something isn't connected properly. The fact the switch won't reset it, I feel maybe this units button isn't properly working.