You can only book UA metal on the website.

You have to call to book or create an ANA FF account and you can check Star Alliance availability. It has always matched UA availability in my limited experience.

6/7 has no availability in IAD-CPH. But you can go via London on any of the UA flights, for example.

To me it is unfathomable to book an airline ticket one year in advance. I usually have good luck booking SAS C class with short notice for awards. I am sure that they only make a small fraction of inventory available on this route one year in advance and it gets snapped by the one-year-in-advance-hunters.

Also, SAS is cutting back C class seats on the 330 that serves IAD when they install sleeper seats.