can't sign in to account on itunes app store

I'm using my iPad 3 w/ wifi. It was working fine until suddenly I couldn't connect to the iTunes store. A pop-up just keeps coming up saying "Cannot Connect to App Store." Now I can't update apps, view purchases, etc. I tried everything posted in other threads and none of them worked. I tried resetting everything, changing the date, even changing the brightness, and changing the wifi DNS, etc. I know it's not the internet connection because I can go online easily.

The same problem occured on the iTunes in my laptop. I have updated to the latest iTunes but after I enter my information to signin, "Accessing iTunes Store" is continuously looping. I have tried resetting the cashe as well as the parental control thing but nothing works. All the threads I find are from a few years ago and don't work at all.

What should I do? I'm pretty sure as long as I can sign into my iTunes on my laptop and access the app store, then the problem should be fixed for my iPad as well.

Please help! Thanks.

_Edit

When I clicked to stop accessing the iTunes store on my laptop, the pop-up said "We could not complete your iTunes store request. An unknown error occurred (-50)." if that helps.