Howto break Prima Volta over 2 pages

Your question is not really clear, but if you mean that you want to extend the volta line over to a 2nd page, just keep extending it via shift/right arrow.

I'm guessing maybe you've been trying to use the mouse to drag a volta line. That's not the right way to extend it, whether or not it needs to go to the next page. You need to use Sift+Right or it won't play back correctly or render correctly if the layout should change.