WeChat requires users to complete security verification when trying to log in to WeChat on a new device, please complete the new device login verification according to the prompts.
If you fail to pass the verification,
(1) Tap Unable to Log In? at the bottom of WeChat login page and follow the instructions to submit your request.
(2) After submitting a request, you will receive a result via SMS within 24 hours, if your request is approved, a new WeChat password will be sent via SMS.
(3) Login WeChat via entering WeChat ID and new password.
For more information, please check: https://help.wechat.com/cgi-bin/micromsg-bin/oshelpcenter?opcode=2&lang=en&plat=ios&pid=1003374&id=160115znmzma160115frv6fe&Channel=helpcenter