Q: Applications on itunes store wont download??

Hello, I have been experiencing trouble with my Iphone. None of the apps, in the app store, will load! It doesn't matter if it's an old app or new app, it is not highlighted and I cannot click to load the app.  Also, when I try and make a purchase to upgrade an app, it says cannot.  I have logged out and logged back into itunes and it would not fix the problem. I also did a cold reboot on my phone and it did not help the problem either. I'm sure it's a glitch! Can anyone can advise of what else to try?