None of the US carriers have PE. at least as you know it, on this route, so you are either in J or Y and maybe you can talk LH into rebooking you into at least a better seat (all with fancy names).

You could ask to be rebooked on UA or AC, connecting onwards to DEN. Alternatively, price out a new ticket on anything you want and see if it comes close to what you have paid for the current ticket. You are, of course, entitled to a full refund of that ticket.

As fair warning to others, always have your alternatives in mind. It is a lot easier to get the rebooking you want if you are able to read off the exact routing.