Change the network or wait patiently. According to relevant information, some network operators do not support logging in to the New Beijing Forum, so they need to change their networks. In another case, the copyright in it has been taken back, so it can't be uploaded for the time being. You need to wait patiently for the forum administrator to repair the forum.
Beijing Forum is an international academic conference jointly sponsored by Peking University, Beijing Municipal Education Commission and Korean Higher Education Consortium with the approval of China the State Council and the Ministry of Education and the guidance and support of Beijing Municipal People's Government.