Raspberry Pi 4B putty connection network error: connection refused personal feelings and solutions

Raspberry Pi in the connection process suddenly discovered the connection failed, tried everything online, or does not work.
Under the new boot ssh file does not work, there are circumstances under screen, you are prompted to access is not enough. Under no circumstances when the screen (about to SD card into your computer) file and create a new ssh wpa_supplicant.conf file, then the SD card into the raspberry pie, raspberry pie or automatically delete the new file.
I found that when using the Raspberry Pi, its IP address is constantly changing, to find its IP on all normal.
The picture is Finding Raspberry Pi IP command when the screen. (Inet is the Raspberry Pi's IP address)

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{Initial use some of the feelings of Raspberry Pi}