I updated to iOS 8 and apple ID says "could not sign in an unknown error occurred"

So as the title says, I updated my iPhone 5 to iOS 8 this morning and haven't had any issues all day until I went to the app store and tried to purchase an app. When I tried to install a new app an alert popped up that said "could not sign in unknown error occurred". I completely closed the app and tried again but it still didn't work, I tried signing out of iTunes/app store and it wont let me sign back in, just gives me the same alert. I googled it and tried the solutions I could find and nothing has worked so far....I have completely rebooted my phone twice and still nothing.

can anyone help with this one?