What does PPPoE Connection Error 651 mean?

PPPoE Connection Error 651 is a common Windows error message that indicates a problem with your internet connection, specifically when trying to establish a PPPoE (Point-to-Point Protocol over Ethernet) connection. It typically means that your modem (or other connecting device) has reported an error to Windows, preventing the connection from being established. While the error message itself is generic, it points to issues ranging from physical cable problems, modem/router malfunction, network adapter issues, or even problems on the Internet Service Provider's (ISP) side.