We have no internet service to our home except a strong Verizon 4G LTE signal. So we use a new MiFi router for internet (https://www.verizonwireless.com/home-office-solutions/verizon-lte-internet-and-home-phone/#sku=sku1980155).
I set up 2 brand new Play 1s on this device and everything worked great, but the next day the Sonos system lost connection. All other internet devices are connecting without a problem. When i opened the Sonos app it asked me if I wanted to set up a new system or connect to an existing one. Clicking "connect to existing" caused the app to search and then fail to find any system. I tried this numerous times, eventually tried "set up new system", that didn't work, and after messing with it 60 times it suddenly connected again and worked fine. A few hours of music later the same thing happened - it's like the Sonos system disappeared.