My first impression of this is that it is a very clean, eye-pleasing image.
Compositionally, it has some interest with the "flowing" left to right, and that being almost, but not quite, exactly "set up" by the lighting (?) in the background.
I also like the "stacking" of the grays. It gives it a graduated feeling, and makes it feel more stable on teh bottom of the shot.
The only "nitpick" I can find, is that it is a bit "flat" in subject. No pun intended. There is little or no feeling of depth to it. Whilst that may have very well been your intention (and I honestly think it sorta works here), the voter's may have been a bit put off by that (but with a score of 6.1ish, it's nothing to be ashamed of. :) )
Good work, and best wishes in future challenges.
karmat