Check out this article, it should provide some answers. If not, try this solution which other users found helpful:
Please follow the steps below to resolve this issue:
- Check your email application's spam or junk folder or filter. Please be aware that some emails may be blocked by your ISP (Internet Service Provider).
- Check that you're trying to log in from the exact email address you registered with. A common error is registering with an incorrect email domain (e.g., @comcast.com is not the same as @comcast.net).
This is the form to use: https://www.facebook.com/help/contact/?id=221689587951755
Let me know if this helps,
Content Editor and Community Manager - CCM.net