I had been constantly been playing MCC without being afk or using bots. I was banned two days ago and when I got back on I had been banned for a month.
If you have been playing Grifball and have been constantly killing AFK players and/or sword lining, that counts as boosting and therefore is grounds for being banned.
If you feel that you have been wrongfully banned, however, you can send a support ticket.
Please use the ban thread pinned at the top of the forums for any queries on matchmaking bans