Why can’t I update YouTube on my iPad mini?

I’ve recently tried to go onto youtube on my iPad mini. It comes up with an Icon that says the app needs to be updated,otherwise I cant Use the app. but when I go to the App Store the blue button turns white which doesn’t allow me to update. I have deleted it and tried to re download it but it’s not downloading now. I have plenty of storage so it can’t be that.Help?