This is what i suppose to day which he do already sent those bitcoin on older address but ive been using ccex in the past , your btc wallet wont change if you didnt remove or tend to change it maybe op do change that and forgot that one and instead of sending the bitcoin to the new wallet address he do send on the older one which wont really be credited on his account.
C-CEX itself reset their BTC address due to some reason and it announce to their twitter official account. What I'm confused here is the timing of the deposit OP is sucks.
The only thing he can do is create a support ticket and I'm sure that C-CEX will accept this because their reset of BTC address is not announce officially on their site a week before it is done.