On December 1st, 2018 NordVPN’s servers stopped supporting L2TP/IPsec and PPTP connections.
NordVPN aims is to provide top-notch security and privacy standards to our customers. As the Internet and technology world rapidly advances and moves forward, we witness a tendency that users are shifting from using outdated, inconvenient encryption solutions to more advanced ones. L2TP and PPTP protocols are largely obsolete. Because they are so insecure, they have become incompatible with a key part of our core mission – to provide our users with industry-leading security.
You can read more about that on this article: https://nordvpn.com/blog/l2tp-pptp-protocol-update/