Apple App Store (install and get) loop, how to fix it?

I figured out that the problem came from fingerprint (Touch ID), as when I turned their options off, it worked like charm.

Just turn off those settings under "Touch ID & Passcode" section: 1. iPhone Unlock. 2. iTunes & App Store.

I just confirmed from Apple Support Center that it cannot install apps even free ones if there is not a credit card on file.

So, if not, add the credit info and shipping address to your apple id in advance.

I had the exact same issue on Mac App store when I tried to download a free app. It was looping between Get and Install. I tried all the above mentioned suggestions but what worked for me was signing out from my App store and logging back in.