I think you may need to call 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.

For further reference, I might suggest posting here in your own language:

https://en.community.sonos.com/sonos-nordic-forum-229118
 

Try unplugging the speaker for about 10 minutes before you try to reset it again. Sometimes electronics need a longer time being powered off to clear things out