1. Delete and then reinstall the Facebook app.
2. Login with account details.
3. On the security page that opens up, select “Get help from friends”.
4. On the trusted contacts page that opens up, select a few good friends who you can contact easily.
5. Click on Continue. Facebook will send a security code to all the friends you have just selected.
6. Contact those friends and request that they send you the code.
7. Once you gather all the codes from your friends, you can use the code to unlock your Facebook account.
If that doesn’t work…
1. Reinstall the app on your phone, and clear the cache if you have it opened in your browser.
2. Email firstname.lastname@example.org and include your name, date of birth, and a brief description of the issue. They will likely ask you to confirm your identity with a license or passport.
3. Once your identity is confirmed, they will send a reactivation link as long as you have not violated any of their policies. Click on that and go through the automated security verification process.
4. During this time, try not to attempt to open your Facebook account for any reason.
To make sure your account doesn’t get locked out again, verify your account here.