I know there have been quite a few people with deposit issues and other problems with Poloniex the past few days. Currently, the wallets are disabled.
I Would recommend holding off on depositing to Poloniex. There are some rumors going around but a post 
https://steemit.com/bitcoin/@kingscrown/latest-news-from-bitcoin-exchanges
There seems to be a big backlog on a few exchanges so take caution for the time being.
This situation seems to be affecting a quite a few people and even with withdrawals.
https://bitcointalk.org/index.php?topic=420836.2140
With the growing amount of adoption of crypto, the influx of users could be the cause of these delays. Let's hope that's what the problem is.
Currently it's recommended by many users to use Bittrex. I sent some SBD there yesterday and came through quick with no issues.
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