The black screen may be due to too many applicants, resulting in system congestion or abnormal network. The former can refresh the phone and wait patiently for a few minutes, while the latter needs to switch networks to keep the network open.
The implementation of "code scanning authentication" is not only to improve the convenience and experience of the general public in using health codes, but also to ensure the authenticity and effectiveness of health codes on the basis of preventing epidemics.