How were the speakers connected before?
If you are using wifi on new router, is the signal strength ok? 2.4G or 5G?
Have you programmed in the new wifi network name and password?
Does the speaker have an ethernet port to test it on? Removes wifi complications.
Are there any error messages in the Sonos app? Does the speaker get an ip address?
What other things were suggested from Sonos support?
Where does the speaker get its music from?