802.11ac support?

To Chock: Your problem sounds very familiar to me and I wasn't able to resolve it with any info I saw on Sonos support page or in the community groups. I did however solve the issue I was having. I'll outline the problem I had and the solution I applied, in hopes of getting your music back.
Hadn't used my Sonos for quite some time, and wished to do so. Having moved it briefly to another network last use, I had to re-establish connection to my home network. Not thinking, I used my 5ghz network and the Sonos software used it just fine to establish that I needed to upgrade, but the upgrade failed due to the factory of 5. Switching to 2.4 have no joy, and could not establish connection to the device.
The solution lay in the failed update.
First step was to be connected to the 2.4 on device you have the controller/Sonos app installed. Then using whatever flavor application manager your OS uses, find Sonos app, storage info, and "clear data".
Then refire the Sonos app, should then detect and successfully update the device over 2.4 and connectivity issue will vanish.

I used my 5ghz network and the Sonos software used it just fine to establish that I needed to upgrade, but the upgrade failed due to the factory of 5.
There may be some confusion here. Sonos units can not connect to a 5GHz WiFi in 'Station'/'Standard' mode. And a Sonos system in 'SonosNet'/'BOOST' mode is wired to the network, so it doesn't matter whether the controlling device is on 2.4GHz or 5GHz.

If a system is in 'Station'/'Standard' mode it's connected to a 2.4GHz WiFi. There are instances where a controlling device on 5GHz is then unable to discover the players. This is because a router is not correctly forwarding the discovery multicasts between its two wireless segments. Behaviour is router-specific.

Ratty: No, but the controller app does a firmware version check when launched and can access the web to do so regardless of which band it's connected to. If a new version is detected though, and the device running the controller is connected to 5ghz band, the update fails because the Sonos itself doesn't speak 5, and connection fails even if you switch to 2.4. The version check/failed update seems to corrupt the version database somehow as the check and notification is not repeated simply by switching to the proper band. Clearing the data allows the update to occur successfully and normal connection to resume.

Sonos , was it really that hard to include the ac chipset in the sonos one? Seems sloppy , to me.

Sonos , was it really that hard to include the ac chipset in the sonos one? Seems sloppy , to me.

Why would you need 5Ghz? Do you know it has far less penetration through walls than 2.4? This would be disastrous for many sonos users due to the distance limitations of 5Ghz.