It sounds like you have booked a travel agency issued discounted group ticket.
For these heavily discounted fares, advance seat assignments will not be made by the Tokyo Elite line staff.

I have had this experience trying to get an advance seat assignment on this type of fare on several occasions. The policy is not to preassign seats, despite elite status, as the bookings are technically part of a (discounted) group booking. This is how they are able to offer the cheaper fares than those which are available through normal www.nwa.co.jp for example.

Anyway, as suggested, I would call the Elite number in the States and get your advance seat assignment that way. This is what I usually do.

It is frustrating not to be able to do it through the local office. Personally, I don't think it is shoddy service by the Tokyo Elite line staff. It is a policy that many airlines adhere to due to these very specific fare types.

------------------
NW Platinum Elite, SPG Platinum Preferred