I'm following on this with a somewhat similar issue as OPs -
Booked MU tickets through their website, received confirmation e-mail with Order No and 781-stock tickets number.
Managed to get to the Seat Reservation Section of their website, logged in with TicketNo and Pax name, got to the Seat Reservation page but when i click on the Seat Reservation link, i get this popup:
"Seat reservation is unavailable for this flight segment. For specific reasons, please refer to China Eastern Airlines Booking Notice on Passengers for Seat Selection below. Online seat reservations are not available for international routes. Please go to the airport check-in counter for this service. Thank you for your understanding."
Flights are domestic (PEK-SHA-PEK).
Any advice?
Thanks!