I stopped using Spectrum’s devices, other than as a modem, within days of setup, just as I didn’t trust them. 

I’d wager they sent an update to your router without your knowledge, and that messed up your Sonos system. 

Hi @Mkempken 

Welcome to the Sonos Community!

I’m sorry to hear of the issues you’re having with your Sonos system on your Spectrum internet. I recommend you get in touch with our technical support team who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports - you should get some definite answers.

I hope this helps.

Spectrum router caused all the problems with mine. I kept their modem and exchanged the new "latest" router Spectrum gave me with a TP Link 4 Mesh ($90) and all works now. Fought same thing you were for 2 months. I finally found something in the Sonos site that says Spectrum routers don't work. I set up the TP Link, gave it a new wifi name, got it set up, then renamed it to the old wifi name, and all my devices found it. With Sonos, you will need to go back and find the newer speakers (ERA, SONOS 1) but my play bar and sub automatically were found. I can't believe they don't do a mass email to account holders with this tip.