Ok, if I've got the sequence right then:
You tap on the iTunes Store app.
It opens iTunes U, and says "Open iTunes U"
You tap on something (or nothing)
And it eventually says "Cannot Connect to iTunes Store"
Honestly, I'm baffled. I can't think of any reason the iTunes Store would redirect to iTunes U; especially when you don't even have the iTunes U app installed.
This is my suggestion.
Go to Settings > iTunes & App Store, tap on your Apple ID, and sign out.
Reset the iPad (just because it might help)
When the iPad finishes restarting, Open the iTunes Store again (without signing in) to see what happens.
if it goes to the iTunes Store as it should, then
Go back to Settings iTunes & App Store and sign back in
Try opening the iTunes Store again and see what happens.
Good luck.