I’ve has issues with my Sonos setup since installing it. It would sometimes disappear from the network, sometimes the app wouldn’t see the system etc. Today (after more than a year of disappointment) I was guided through an hour-long debugging session by the very helpful Jenny, which changed the following ASUS router settings from their defaults:
Advanced settings > LAN > IPTV > Enable multicast routing
Advanced settings > LAN > IPTV > Enable efficient multicast forwarding (IGMP Snooping)
Advanced settings > Wifi > Professional > Enable IGMP Snooping
Also, check if the firmware of the router and mesh nodes are up to date, and whether the Sonos app displays any other (old/concurrent) Wifi networks (otherwise the system might keep switching back and forth).
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