It's as the others said, you cannot use the over-the-air (OTA) function on a jailbroken iPad. Fortunately, it just won't work (cause if it did, you'd mess up the iPad...).
If you want to upgrade your jailbroken iPad, you will have to use iTunes and you can only upgrade to iOS 7.1.1 - and that iOS is NOT jail breakable.
But, if you've decided you want to go back to stock, simply connect the iPad to iTunes and press the Upgrade button. Make a backup first so you don't lose your app data and other iPad settings!
iTunes will do its "magic" and when it is finished, your iPad will be running iOS 7.1.1.
Good luck and let us know how you get on.
Marilyn