I can’t download apps

I have this problem

1: I open the apple store and click an App I want to get (usually free)

2: I click get and the app info tab appears

3: I enter my apple password and tap the sign in button

4:the button darkens as to signify I tapped it but doesn’t respond and the question mark button does the same , the only button that works is the “cancle“ button

How do I fix this? I’m also supposed to have a little box that will ask permission to download the app to show up and it never does .