Maybe the time is too close. Without signing the online license, HowNet cannot include the contents of the paper; Confidentiality is commercial value. Some parts are sensitive and involve national defense and national security. If it is confidential, it will definitely not be published online. Other parts of the paper have commercial value, and public publication on HowNet may infringe upon interests.
Core journals are not on HowNet. A few core journals have not signed an agreement with HowNet, and some fake journals can't be found on HowNet. The author's paper must be submitted to regular journals. If it is a fake journal, then the paper is definitely not available on the Internet.
Database providers need authorization from their schools to include their papers. Many universities are unwilling to submit their dissertations to the database for inclusion, so naturally they can't be retrieved. Because some papers are not included, sample papers mainly provide paper information through cooperation with periodical circles, publishing circles and content providers, so some journals that are not included may not be found online.
Use the school intranet, because the school paid for China Knowledge Network. I have encountered a similar situation if I can't download files from home or Internet cafes. If you can't use the intranet, there are several situations in which you can't find the graduation thesis on China Knowledge Network, including: the thesis is included in the self-built database of our school; The graduation thesis of master's and doctoral students belongs to classified thesis; The paper is in the transition period of collecting papers and has not been included.