The U.S. Copyright Office has been moving DMCA registration from paper forms to an online registration system. All previously filed paper DMCA agent registration forms expire on December 31, 2017. U.S. ISPs and non-US ISPs doing business in the United States should have re-registered using the online DMCA electronic registration. If you've neglected to register using the online system, you have until December 31, 2017. https://www.copyright.gov/newsnet/2017/694.html