Old devices verification code

Hi,

I met on 2 old devices (analog) hvi-sv & hwi-sh the below issue.
Two different devices at separate places , with latest firmware version 3.1.4 , try to add on hikconnect or ezviz appears online but verification code is false if i put ABCDEF ..There is not verification code under the device and it never change before..I can not change the verification code too..
Have you any idea about it?
Thank you