Are you linked to the internet? Haha, seriously however, are you?
Presuming you have the appropriate login e-mail and also password (as well as you're attached to the web) there's a couple of things that may be triggering your troubles:
Can't Login to Facebook
Are you getting an error message? If so, examine the Facebook help page for explanations and fixes to well-known concerns.
Ensure you do not have any kind of expansions or antivirus programs running that are blocking Facebook.
Have you attempted getting rid of the app's cache? Most likely to Settings > Applications > Facebook > Clear Cache. If this does not work you can try cleaning data also and also as a last option uninstalling as well as re-installing the app completely.
Did you sign up with your phone number? See to it you key in the country code also when logging in.
If the application is telling you to upgrade your email address, this is probably because your e-mail server is classifying your Facebook e-mails as spam.
If you have actually recently enrolled in Facebook you could need to confirm your account initially. If you've lately changed your password, ensure you're trying to visit with the new password and also not the old one.
If you're logging in via an internet browser, make sure you have cookies made it possible for which facebook.com is added to your checklist of risk-free websites.
Make sure you have one of the most recent variation of the Facebook app for Android.