Try fixing that white line off to the right side of the image, like greenraven recommended.

Also, you can push this a lot farther. Think of EBoy - his stuff has so much detail you can look at it for hours.

Thanks I'm going to try and align the windows and put some more detail in Its quite annoying its the 4th piece of pixel art I've submitted to this and all of them have needed revision.  I think someone has something against me lol.

EDIT: I've now revised it and aligned the windows and put some more detail in it

this could need a whole lot of work, its way to simple now. try adding more details, actually thats the fun part of iso pixeling imo.... for instance, add some trash, posters, graffiti, curtains, plants... and so on...., the windows arent aligned very well, and somehow they look like old computers...you should get rid of the black lines aswell, at least for the inner parts.... contrast could be higher too

There's a white line off to the side of the building.