Why can't I download snapchat from the App Store ?

Since my snapchat wouldn't open , I delted it and tried to download it again from the App Store. It shows a circle with a square in the middle like it's updating or downloading again , but it doesnt doesn't show on my home screen that it's downloading again . Sometimes , it sshows a cloud with an arrow pointing down and I click it and it says that there wouldn't be an additional charge since it was on my phone before , but it still won't download . What can I do to fix it ?