If it was something simple such as document settings, or a quick fix, then they would issue a “Soft Rejection” and tell you exactly what the problem is before letting you submit it again. In this case, it was “Hard Rejected”. For these types of rejections they aren’t able to give a detailed explanation, simply because of the sheer number of submissions they have to go through every day, it just isn’t possible to give detailed feedback on every item while also keeping review times as low as they are.
As for the item itself, it’s pretty good. I especially like how the majority is unique design elements, rather than relying too much on photos like so many others do. For this reason alone I think you’re on the right track.
For me I think the two main issues would be that I’m not really sure exactly what this flyer is trying to achieve, and the hierarchy isn’t really clear with it all mostly being the same colour, and being overall quite flat.
You need to have a clear concept. Yes, you say it’s a corporate flyer, and the overall theme is “chill”, but what’s it for? A corporate event? A proposal? An advertisement? What is the diagram with the mountain trying to indicate? It’s hard to understand what I would use this for, it should be clear as to what it’s trying to show, especially when this sort of thing is likely going to be given to a wide variety of people who will mostly just use it to get some quick information.
I get that the theme is cold and chilly for the winter season, but at the same time it doesn’t feel welcoming, it feels cold. I think you should use some warm contrasting colours, such as yellow, orange, red, and pink, to help highlight the important things, and to draw more attention, perhaps even using the same gradient look, because right now with it all being the same blue/turquoise colours, it’s very plain and flat, so I’m not sure what’s important or where I should look. Plus having some warmer colours will look more inviting, almost as if it were indicating that the important stuff is warm and cozy in a cold and chilly environment.
It’s hard to critique the hierarchy without knowing what the flyer is about, so I think the first step would be to rework it so it sends a clear message. While also trying to use some different font styles, such as a serif font for titles, and sans-serif for body text. It looks to me like it’s all the same font family, just different weights, which also adds to the overall flatness.