I can't install an application downloaded from the App Store?

So I've recently downloaded the YouTube app for the iPhone via iTunes in my PC. However, after I plugged in my iPhone, it won't install! It says "Will Install" behind the app but the syncing will stop. I tried to download the app again, restarted my iPhone but the same result applies. Any good solutions for this?

I use an Iphone 4S.
I download all apps from the app store on the IPhone 4S.
I don't install apps on my PC for my Iphone 4S.
I hope I helped you.

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