For me, I had a very substantial amount of money on Poloniex, none of which I have been able to withdraw since over a month ago.

I've been able to withdraw from Polo, but I'm withdrawing small amounts at a time (less than half a bitcoin).

I think they're manually approving large withdrawals, so do small withdrawals every day instead (it will cost you 10,000 satoshis in fees each time, but that's a pittance to pay to get your money out).

I've heard too that old accounts are having no problems with withdrawals but newer accounts afre struggling.