I can't log into Facebook Through Safari now that I have the app

Please help.

I can no longer log into Facebook through Safari on my Iphone 5s. I recently got the app and that seems to be when the problem started. The app works as does the messaging app. However, when I try to connect my Instagram app or Twitter app it doesn't let me log in. I've tried changing my password, erasing my safari history and erasing the passwords saved in Safari. Nothings worked.

Any suggestions.