Can't download Videos app from the App Store----download icon (blue cloud with an arrow) grayed out.

I bought a new iPhone (ios 10.2 beta 7 )before couple days. When i was importing photos and videos to the iPhone from the computer, the photos were imported but they asked me download the Videos app from the App Store, after i downloaded the app (day 1) the videos were automatically transferred into the Photos app. And then I deleted the Videos App. But now ( day 3) when i want to download it again from the App Store, the download option was grayed out, when I try tapping on it nothing happened. Can anyone over here please help me? I have no clue how to transfer videos. And the videos which I wanna transfer are not like song videos , they are like casual pics--snapchat videos, etc...

ANYONE PLEASE HELP ME...😢😢😢😢😢