What is it to log in to WeChat and prompt to scan the code to verify identity?

This should be because your WeChat account has entered protected mode, and two conditions are needed to remove this mode:

Select no less than 1 from the list of alternate friends for verification, and then contact your WeChat friends and tell them the verification code, so that your friends can send the verification code to your WeChat via WeChat.

Select more than 2 friends to send you verification codes, which can directly turn off account protection. If only 1 friends are successfully verified, the account protection can be released after 24 hours.