After moving over to giggaclear fibre broadband every smart device connected to my new Linksys mesh giggaclear router except for my sonos soundbar and seperate speakers. Days of trying to reconnect did not work. Today I have spent 4hrs speaking to broadband provider and finally sonos support.
For anyone else who has a similar problem here is the fix. Sonos Only likes connecting to 2.4ghz where the new router sends out 5ghz. Speak to your broadband support and they will show you how to split the 5ghz and 2.4ghz into two separate networks, this is actually really simple and I'm no tech head.
Then make sure your sonos app has the latest updates.
Factory reset each sonos product (do this one at a time) - Instructions on you tube for this very simple.
Then the device you use to open the app make sure it is connected to the 2.4ghz connection (rename this your sonos 2.4ghz connection)
Go through the new set up instructions and it will work. Apply this process to each sonos product you have. It worked for me. Sonos support were amazing. Horea your a superstar he was patient and was on the phone to me for nearly 1hr trying to work out all the issues i had which i won't bore you with.
Anyway good luck.