As title says - while rare, at random the game just fails to connect as if there was no more internet on the device. You see the red ping notification and if you try restarting the app, it gets stuck early and reports no connection.
However, everything else on the phone that requires internet works just fine. The only solution is to actually restart the phone and hope you get a different connection path of sorts? My educated guess here is the DN servers run on multiple nodes and this is the result of at least one of them failing.
This is obviously extremely game-breaking when it happens mid-drs or mid-bls.