Are you linked to the net? Haha, seriously however, are you?
Assuming you have the right login email as well as password (and you're connected to the internet) there's a couple of points that could be causing your troubles:
Facebook Mobile Login Page Problem
Are you obtaining a mistake message? If so, check the Facebook help page for descriptions and fixes to well-known issues.
See to it you don't have any expansions or antivirus programs running that are obstructing Facebook.
Have you tried clearing the app's cache? Most likely to Settings > Apps > Facebook > Clear Cache. If this does not function you can attempt clearing information as well and as a last resort uninstalling and also re-installing the app completely.
Did you sign up with your telephone number? Make certain you type in the country code as well when logging in.
If the app is telling you to update your email address, this is more than likely due to the fact that your email server is classifying your Facebook e-mails as spam.
If you have actually lately registered for Facebook you might require to verify your account first. If you've just recently transformed your password, ensure you're trying to visit with the brand-new password and also not the old one.
If you're logging in by means of a web browser, see to it you have cookies allowed which facebook.com is included in your listing of secure sites.
Make sure you have one of the most recent variation of the Facebook app for Android.