Best answer by Edward R
If you are still having issues maintaining connection to one or more Sonos devices, sometimes, it's as simple as turning the router off for a few seconds. If this doesn't help, below you will find some useful content that we strongly recommend reviewing.
This article, that talks about Speakers disappearing or dropping off controller. This is an issue commonly caused by WiFi interference.
If you are still having issues, you may wish to get in touch with our support team via telephone.