Not sure, but you might have been banned. Did you use the high damage mod in the GEX map? It's just possible cause that's the same message that I got when I was banned.
GEX means guild quest ex, it was the recent guild event before the maintenance. If you attacked in this event while the high damage mod is switched on you'll be banned.
View attachment 499390
GEX means guild quest ex, it was the recent guild event before the maintenance. If you attacked in this event while the high damage mod is switched on you'll be banned.