Facebook App: login error an unexpected error occurred. please try logging in again

I have had the exact same issue! Facebook deactivated my account as well in July. I've determined I was hacked. It was linked to my instagram which was also locked out and I caught my twitter account before the hacker had changed the password. But they had changed the persons name, email, address and phone number just kept my sign in username. The person was a Russian female with Russian address and phone! I can only assume that this was the same person who hacked my facebook. I've been trying to get my facebook account back ever since. When I tried signing on with a different email, it linked to my mobile number and locked me out there as well. Finally I was able to get a new Facebook account with a new email address, changing my birth date and my name slightly and not listing my mobile #. I can now sign in from my computer, and my mobile Safari browser, but NOT from the Facebook app. I tried cleaning out the cache and cookies, but still get this same message from the app. Reinstalled the app- made no difference. I did download the Facebook LTE and had no problem signing in...so I do think there is a cache I was not able to erase on my phone which does make it an apple communication issue. I would like to find an answer!!