A major issue which is being faced by a lot of people nowadays is that they find it very strenuous to log in to their account once it gets locked due to security reasons. Although thinking from the client's point of view it is at a positive side because the client doesn't want the user to face any problem in discrepancy of his/her data or someone else accessing their account.
Solution to Facebook Confirmation Code not working:
For this reason the concept of confirmation code is designed, so that the user can only access his/her account with the help of the confirmed and updated phone number and email address. Sometimes even if the user is trying to access the personal account but it gets locked out due to reasons stated in the privacy policy of the firm, people find it difficult to log in.
The text above is a summary, you can read full article here