1. Bad network or faulty mobile phone. If it is a network problem, you can try to change the network; If there is something wrong with the phone, you can try to restart it.
2. The software itself fails, such as system crash. In this case, we can only wait for the staff to restore the system.
3. There is a problem with health status, that is, holding a negative certificate of nucleic acid test within 48 hours.
Please note that the above is only one of the possible reasons, and the specific reasons need to be judged according to the actual situation. If the health code is abnormally unavailable, it is recommended to contact relevant departments for consultation and solution.