Installing stopped and can’t continue

So i tried downloading null’s on my IOS phone and it went well but wen i came back from school the installing randomly stopped and i couldn’t instal again. Does anyone else have this problem and how do i fix this?

Ensure you have downloaded the correct file for IOS.
The link is official.
Also, follow this guide to learn how to install the app.

Downloading from unofficial places like (Don’t install from this link.) Unsafe may be dangerous for your device.