I called 3 different agents.. all told me the same thing:
seat is blocked by check-in. They sent a message to the check-in ppl that i would like that seat, or the seat may be released 24 hours prior to the flight and I should check back then.

They explained to me the set of seats set aside like this differs from flight to flight, and there is nothing they can do to unblock.

I tried the German and the US SEN number.