Reply from Polo:
Unfortunately from time to time our wallets require maintenance to ensure their continuing functionality and security. I understand this may be frustrating but unfortunately this is just the nature of such wallets, which can be temperamental and require much TLC to be kept running smoothly.
Any deposits you have made will be safe on the blockchain and will be credited as soon as the wallet is active again.
Once the wallet now re-enabled it should be functioning as normal and all your withdrawals will go through. Thank you for your patience and understanding.
Sincerely,
Poloniex Support Team