The main reasons are as follows: 1. Data upload delay. Generally, the results of nucleic acid testing by yellow code personnel can come out within 4-6 hours at the fastest, but if there are a large number of people, the results will be delayed, which will also lead to the delay of health code data. In addition, generally, the green code will be slightly later than the nucleic acid negative result report. It is recommended to wait for a while and reopen the small program to check. 2. Abnormal nucleic acid results. For example, when personal information is wrong during nucleic acid detection, personal nucleic acid results cannot be issued. At this time, the health code cannot receive the certification data of nucleic acid negative, so it naturally cannot be transcoded in time, or the nucleic acid results appear false positive or positive. At this time, there may be a risk of infection, and it is necessary to recheck the nucleic acid confirmation again to eliminate the risk, so it cannot be converted to green code. 3. Although the nucleic acid test results of some people with changes are within the 24-hour validity period, due to the changes, they are in line with the list of people who have been given yellow code again. At the same time, the last nucleic acid sampling time was earlier than the yellow code time, so it is still yellow code. At this time, after the nucleic acid sampling result is negative, it can turn green. 1. Call and ask about the nucleic acid results. If the results are all right, just wait patiently. 2. If there is a problem with the nucleic acid result, take isolation measures and check the nucleic acid according to relevant requirements. 3. If it&;s yellow coding again, it can&;t be used as the basis for turning green due to the results of previous sampling, so it&;s necessary to conduct nucleic acid detection again.