I had trouble with a withdrawal because I use VPN and thus IP adresses change all the time. This was a signal for Poloniex to freeze my account. Despite the fact that I used my password and digital code.I had to renew the identification protocol. To my opinion this is all a bit too much. It seems that if you use VPN, you cannot make crucial deals, because your account might be frozen. On the other hand it is good to be alert and take care for your customers. In the end Poloniex restored my profile.