1. Does the LED light up? If so what does it do?
2. Have you tried hardwiring it to your router? This could help get it reconnected if it is powering up.

Hi thanks for you quick reply. Yes the led is on and is colored a whiteish blue. If I press the buttons it will flash yellow and return to the first color

You’ve been very helpful, thank you very much!

My SONOS 5 gen1 won't connect to wifi or Ethernet cable. I did the factory reset. When I'm pressing two buttons, mute and volume down together, red light is on, than orange light and white. They are changing. My app S1 is searching for the device but no way it can find it. I am desperate. Please give me some advice. 

Thanks, Alex 

I would recommend that you submit a system diagnostic , and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they get sensitive about GDPR.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

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