I think the reason for blocking your account is multi account.
Yes, that's the reason why they banned his account according to the customer support reply.
However, in their FAQ they say that alt accounts are allowed,
unless it's used to cheat or abuse their bonuses:
Are "alt" accounts allowed?
As long as you have not created another account for nefarious purposes, that's fine.
We reserve the right to disable accounts that have been created with the intention to abuse our bonus, coupon and chat features.
This is the account of their official representative:
RollbitcomSend him a PM or post on their
announcement thread to get their attention.