Hi, I have attached a rejected photo, due to technical reasons. Can you please give me some advise
Are you sure this wasn't rejected for Intellectual Property reasons? Snowboard designs are protected by the maker. The boots may be protected too. I think you have little chance of getting this accepted for commercial use. Sorry.
The reflection of the girl in the weindow needs a model release and the trademark on the board needs a property release.
The technical issue is the white balance: the snow has a bluish tint. A little warm-up helps. May be with some tweaks to the shadows' area of the histogram.
However, as stated by @RALPH_L and @Nancy OShea, there are several issues that make this picture impossible to get approved, as the snowboard design is iconic. You would need to neutralize the whole snowboard design. Additionally, the shoes also have logos and other design elements. The belt between the shoes is not neutral, neither. Then you have part of a logo on an undefinable something, I suspect a bus or a car in the window reflection.
And finally, there are 2 persons reflected in the window, where one of those could need a model release. It would be no problem for you to get the model release for you, as you are also recognizable in the window.
There is also, in my view, a lack of aesthetic and commercial appeal in this picture. There should be mountains as a background, and the snow should be fresh. I would at least photoshop out the background to insert a more interesting view. But well, except for being a nice exercise, you won't get this image accepted, because of the snowboard design.