This requires finding out which link the problem lies in, such as the post office, the mailroom of your unit, or a friend of yours who received it but forgot to give it to you or lost it, etc. wait. Since notices from the Patent Office are all registered letters, you can check where the letter was sent, who signed for it, etc. Therefore, you can only determine who is responsible after you find out where the problem lies. The Patent Office has corresponding regulations for specific solutions, which can be found on the website of the State Intellectual Property Office.