iPhone Facebook app won't work for my account, but works fine for other accounts...?

[Jason]

I'm using the most recent Facebook app for the iPhone 4s on iOS 5.1.1. Yesterday, I tried to deactivate my Facebook account on my phone. I clicked the deactivate button, it logged me out, but didn't actually deactivate my account. Ever since then, I have not been able to log on to my account from my phone. It works perfectly fine on a computer and on my phone if I use Safari, but not on the actual Facebook App. I've deleted the app and reinstalled it several times. I've power down my phone and restarted it. I've closed the app out. I closed it, deleted it, power off my phone, power it back on, reinstalled, etc, nothing worked. I also tried deactivating and reactivating my Facebook account on the computer. If I log on to someone else's Facebook account from my phone it works fine.

What happens is I'll type in my email and password, it will go to the loading screen, log in, and then go back to the log in screen right away. There's no error message.
Nova, the Facebook App is not listed there. I don't know why.

[Nova]

Find the drop down menu in your facebook account on the upper right corner, from your PC. Clickthat, go to account setting > Apps ( you will find this option in the left side.Find your App. .that is the Facebook app. remove it.. Then again try logging in. When the authencication message comes, complete the required option. It should be done.