Sejun Park, the guy who won the 2014 Pokemon tournament with Pachirisu reports that players who reached Master Ball tier are banned and their ratings erased.
According to Sejun and many other players, when selecting the Ranked Battles a message appears, with the following text: “Communication error, Please start from the beginning.”
Looks like players who already reached Master Ball Tier before maintenance are now all banned from playing Ranked Battles?????
— T1 | Sejun (@pokemon_tcg) December 5, 2019
If you go through the thread and read the comments, the ban is not for cheating, hacking or breaking the rules.
We still investigate the case, and we hope that this is an error and they probably messed something up during the maintenance.