After the first trial of utility model patents, why haven't some patents been issued certificates for more than three years?

Correct it, it should be that the invention is initially qualified! The utility model can only be authorized after it has been examined once and passed! Invention patents are divided into preliminary examination and actual examination. The first trial is a formal review (such as whether the format and documents are complete)! The request for real trial can be made within 3 years after the start of the patent application, which is a review of substantive content (such as creativity), and the patent may be rejected after the review!