Scrap the app and access Facebook from your browser of choice via m.facebook.com - you'll also regain access to Messaging without need of a separate app.
Facebook (and its recent updates) has been problematic for those using the newer OS (Lollipop - 5 to 5.x), so not really surprised if it hasn't broken something when it comes to the older OSs as well.
If you use Chrome as your browser, you can add a shortcut to your Facebook directly to a Home Page.