IPhone Messenger App Not Working?

Recently my Facebook Messenger App on my iPhone 4s has stopped working. It implies that it needs updating as it has faded out and there is a bar which would usually fill up through the process, however when i click on it to update, it simply says: Waiting, and either stays like this doing NOTHING or becomes idle. I've tried syncing it to iTunes to update the app in case the amount of data required cannot be obtained without the internet or whatever, but it's not working at all. Please help!

Try to send images forward and backwards to the iphone, it will work eventually.