Poloniex, the exchange that drives the most volume on a lot of currencies including our beloved Steem and Steem Dollar is experiencing some issues and all deposits to the exchange are delayed and don't show up. There is no official statement over what is going on so until that is fixed, be sure to use other exchanges, next in line being Bittrex (@bittrex), Blocktrades (@blocktrades) etc.
Here's a funny message from one big guy to the other:
Use Bittrex instead, or other...
Until Poloniex sorts it out be sure to use other exchanges.
Be safe today!
PS. Please comment if you've had your deposit go through so we know it's fixed. I'll also update the post when I get updates as I've sent them a support ticket.
LATER EDIT: Transfers seem to have started working again. I sent some test SBD back to my steem account and the transfer was done within a couple minutes.