Why don't some people change the gray code?

I have been to a fever clinic recently, which will cause the health code to be in a state of no code, that is, Gray code.

The following reasons may also cause residents' health codes to be grayed out:

1. A recent visit to a fever clinic will cause the health code to become unmarked, that is, Gray code.

2. The health code turns gray, belonging to people who don't punch in for a long time. Punch in time and do nucleic acid testing if necessary, which will turn into a green code.

3. It is the first time to handle the mobile phone number, and the health code is also displayed in gray.

4. Bad mobile phone network may also lead to health code Gray code.

5. The health code will not be given when the cell is in the closed control area, which may also cause the health code to become a Gray code.