Poloniex hasn't been responsive to any tickets, emails, Slack, IRC, Twitter, etc. about it. There aren't any issues that we're aware of - they simply need to update and enable deposits/withdrawals. Bittrex has been great though - they respond to tickets, do updates in a timely fashion, etc. So, one solution is simply to trade existing XVC on Poloniex for BTC, transfer to Bittrex, and trade BTC for XVC there.