I suspect that you have purchased additional SONOS units or Factory Reset some units. New or Factory Reset units must be added to a system. Likely you setup a new system with these units, rather than “Add to Existing System”. This is an easy mistake. Recovery can be a bit messy.
Note that Factory Reset will trash all room names, music service registrations, SONOS Playlists, and any customizations stored on a unit.
Pick through your systems and choose the system that has the best list of music service registrations and SONOS Playlists. If the systems are registered to different email addresses, this might be a reason to pick the system. This will become your all in one, base system after the following. Do not Factory reset any unit in this base system.
Factory Reset all units belonging to the unwanted systems. Now you can, one by one, add these units to your base system. As you add these reset units to your system, take care to “Add to Existing System”, else you’ll be back in the same soup.
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While you are messing with things I suggest that you go into your router’s configuration and “reserve” or “fix” IP addresses for all of your SONOS units and any regular network clients. This will minimize the risk of future issues on your network. Failure to reserve IP addresses is a major reason users get into the sort of mess that you are experiencing because there were network issues caused by duplicate IP addresses and the users felt that a Factory Reset would fix the issue. In general Factory Reset might accidentally (temporally) work around an issue, but will not result in a permanent “cure”. The factory reset suggested above is one of the few cases where it will be constructive and permanently cure an issue.