My phone hardly ever works these days so I've only just found your replies for which I thank you. I've uninstalled Twitter and tried to reinstall it but it tells me I have the wrong software and am unable to download the app. But there's a growing list of other apps that can't update, quoting error codes which countless others have reported and no fix has been given. I love Windows Phone and would buy another in a heart beat but I've concluded it just ain't worth it. Shame on you, Microsoft
I should add that I've been able to simply log into Twitter using Edge and pinned it to the start screen. It works fine