Why is it sometimes easy to log in to the mobile phone and enter the SMS verification code, and sometimes it is not easy?

In order to ensure the security of the account, when logging in to the cashier for the first time, you will be asked to enter the SMS verification code issued by the system for identity verification. After verification, the system will associate the binding account, mobile phone and mobile phone card. After that, if you change your mobile phone or mobile phone card and log in to PayPal's cashier, you need to enter SMS verification code to confirm your identity. If you still use the original mobile phone and the original mobile phone card to log in, you don't need to enter the SMS verification code.