Quick intro: I haven't really played a pokemon game since Diamond/Pearl generation, so I don't know a whole lot about the ecosystem of the newer games.
My kids both play Pokemon Sun/Moon. They are both obsessed with doing trades in the GTS and I constantly hear them saying they got a shiny Groudon, Latias, Palkia, etc. or what you'd expect to be rare or even super rare pokemon through this system. Usually the trades requested are not of equivalent value. I've heard about the ability to hack pokemon before, but I don't truly know much about it, or if it's possible on the 3DS or only through emulators.
Fast forward to recently, my oldest says he can no longer find people online for battle royale matches. I think he even mentioned he can see people online but cannot directly request battles with them. My other son can still initiate online battles in his game AFAIK. They have both used the GTS and wondertrade the same way.
Is there a way to check if my oldest son's 3DS is banned or if his game itself can be banned from online activity? And what the reason would be for the ban?
Son gets rare/ultra rare pokemon from GTS quick regularly
He can no longer compete in online battles; his brother still can
Can we somehow tell if he is banned from online?