Are you connected to the net? Haha, seriously though, are you?
Assuming you have the best login e-mail and also password (and also you're attached to the web) there's a few things that might be causing your problems:
Facebook Mobile Login Page Not Found
Are you getting a mistake message? If so, examine the Facebook help page for descriptions and fixes to well-known issues.
Make sure you do not have any kind of extensions or antivirus programs running that are blocking Facebook.
Have you tried getting rid of the app's cache? Most likely to Settings > Applications > Facebook > Clear Cache. If this does not work you can attempt clearing up data also and as a last resource uninstalling and also re-installing the app totally.
Did you join your phone number? See to it you type in the country code too when visiting.
If the app is informing you to update your e-mail address, this is most likely since your email server is identifying your Facebook emails as spam.
If you've recently enrolled in Facebook you may need to verify your account first. If you have actually just recently changed your password, see to it you're trying to log in with the brand-new password as well as not the old one.
If you're visiting using a browser, ensure you have cookies made it possible for and that facebook.com is included in your listing of secure websites.
Make certain you have the most current variation of the Facebook app for Android.