This error happens, when the connection to server is not established properly. So, the internet can’t be accessed by the GAME.
This is a CLIENT-SIDE error, this has nothing to do with SERVER. The internet connection is not SECURED in CLIENT-SIDE.

NOTE: Whenever the POKEMON MASTERS TEAM restarts their SERVERS, this ERROR occurs in only few devices and will be automatically fixed after (~1 Day).
But, this can be FIXED on the same day using VPN in mobile device. I personally use SAMSUNG phone and by default it is has SAMSUNG PRO MAX VPN app which’ll do the trick.
