Facebook Chat not working in iphone
Many people have reported that Chat never works for them in the iPhone app. If you try to send a message but the app says it could not be delivered, this usually means that when you were using Facebook on the web you chose to “go offline” in Chat. The problem is that the iPhone app doesn’t tell you that you’re offline, or give you the option to go online, so you’re left confused and thinking that Chat is broken.
you can do following to fix it
you can download app from here.
http://itunes.apple.com/us/app/fchat-for-facebook-chat-push/id386589044?mt=8
or if your chat dosn’t work or it says that you have been timed out go on to account settings and deactivate your account. close browser and start it up again and login to your facebook as normal and your chat should work