Why can't I login to Facebook app.

I have a Samsung Galaxy S5 & I accidently uninstalled facebook app which was working fine. I reinstalled app but now when I enter login details this error comes up .. Login failed. Sorry, unable to login. Please check your internet connection. My internet is working fine & the login is correct as I can access facebook through internet on my phone. Messenger app also won't let me login either.

Welcome to Android Central! We've been seeing a number of complaints like this about Facebook--it seems to be a problem with the app, perhaps with the latest update. I'd wait a few days and see if they push another update to fix the issue.