We purchased a Deco BE11000 Mesh Router (Costco) last month. We changed ISPs from ATT to Spectrum  today. All devices are logged into internet, good connectivity & no need to update passwords or anything. 
When I log into the app & "Discover"

devices, no Deco units show up. I scanned the QR code but with a solid green light, it tells me no further action required.
I monitor my kids' usage & shut down the guest network (their network) when necessary. For now, the app doesn't see any devices. 
I hate to reset everything & have to log all the devices in again, so am hoping for a work around.