Hi @Mac2thaPac.
Thanks for reaching out and welcome to the community!
I appreciate your detailed post outlining the issue as well as the troubleshooting steps that you did, let me help and try to figure this out.
The error message is about checking the network connection, it means that the Sonos app is having trouble connecting to your Sonos products or to the internet.
You may refer to this article provides some steps to follow to get your app reconnected to your Sonos system.
Hopefully, that helps but if not, please submit a diagnostic report when it happens, I'd start by reviewing your system and see if there’s anything causing this issue.
If normal menu directions do not apply when in this state, usually there will be a More Options button, then Submit Diagnostics.
Let us know how it goes and if you have any questions feel free to reach out, we’re always here to help.
The thing is that there is no problem with Sonos. I can play music through TuneIn and manage different speakers and groups. It's just that Spotify doesn't work on Sonos. I can't make Spotify connect work either. But when playing Spotify normally by phone or headset it works perfectly. No issues with the network otherwise. Chromecast, Netflix, Google assistant and Ikea Trådfri works. I did send a diagnostics report because Alla T on Sonos support told me to.