Messenger is not working

If it’s Facebook messenger or any other messenger app that just had an update and requires you have iOS 13 or higher to use it…and you have an iPhone 6 (or any iPhone that can’t get iOS 13 or above) then it won’t work. Your iPhone is no longer supported and many apps have finally stopped supporting the older iOS. If you mean something else please provide more info

Facebook Messenger? Contact their support.