Facebook account login problem may occur due to:
- Logging from different machine.
- Logging successively with different password.
- Logging from different country/places.
- Logging from proxy network: it happens when you try to login through another website or server page.
- Update account setting section: garbage value can make account difficult to retrieve.
- Update your linked email and phone number at account setting: to retrieve password through reset.
To get out of above problem you have to do any of below to retrieve your Facebook account:
- Provide your birthday: it could be an easy recovery option if related field in your account setting not containing any garbage value.
- Identify photos of friends: this option could be little bit difficult if person in your friend list is not much closer to you.
[Account password reset is not the solution here. So you have to do one of above.]
Facebook account password reset : You can request for a new password by clicking the Forgot your password? link on the Facebook login page. Facebook will provide you a reset link in the mailbox.