Unable to install apps from App Store on my iPhone X.

I have an iPhone X with iOS 11.2.6. When I find an app I want on the store and click get, a bouncing message with a small white bar appears on the right of the display (as well as a box at the bottom that gives me the option of canceling the download). Once the bounci message that says “double click to install” appears, I, of course, double click in the area in which the message is displayed. Nothing happens. Ever. The message just continues to bounce no matter how hard, long, often, or quickly I click. If I click outside the specified area, the screen reverts to the underlying screen where I must click “get+” and the whole process repeats. What is happening?