To quote SeatGuru "In Economy, power ports are in every two seats per triple (seats A,B; D,E; and H,J) and one per double (seats A,J). There are no power ports, but there are USB ports at seats 19 C,H; 30 G; 31 A,B,C,H,J,K; 50 A,B,C,H,J,K; and 51 G." You likely got what you paid for. There should have been 2 of 3 operating in your part of the row, though 51E should have been one of them.
There were USB ports for 51 DEG.
In the end, it didn't matter. I'm not complaining because in all honesty, it was the extra leg room in 51 that was the reason I requested that seat.
I'm just trying to provide some info (as well as asking for a clarification) so that Andrew's data is fully up to date for anybody interested.