I wonder if the old link isn't working anymore. That's to say, that it will bring up your booking - but now I can no longer see the fare class on the booking (for an itinerary already booked) against any of the flights.

If you try the LH Passenger Receipt https://www.booking.lufthansa.com/documents?lg=EN it just returns: No confirmation possible.

Kindly contact a Lufthansa Service Center