If you have not received KakaoTalk or text message for 2-Step Verification, please check the followings:
1) KakaoTalk Verification
If you're using KakaoTalk normally but have not received verification messages via KakaoTalk, check whether the account information entered for login matches up with the account information registered to KakaoTalk.
You can check contact numbers and email information in [ KakaoTalk > My Profile > Settings > Profile Management ].
2) Phone Number Verification
There may be delays in delivering text messages depending on mobile carriers. If you're not receiving verification text for a while, tap the "Resend Verification Code" button.
If the "1644" code or "Kakao" is blocked on your phone, text messages containing such keywords may have been filtered out. Please check your Settings information.
3) Backup Email
There may be delays in delivering emails depending on mail service.
If you're not receiving verification email for a while, tap the "Resend Verification Code" button. It could be sorted into Spams or an Individual Mailbox. Please search by keyword, "Kakao" or "카카오," in Inbox.
If you have not been receiving verification emails from Kakao Account, please contact your mail service website to resolve this issue.