hi , i personally do agree with comments in a general way, your buddies do not look realistic enough (what kind be a style also , that’s not a reason for rejection in my view) but the probably is that in the meanwhile, they do not look good enough either. try to think about it, there are already some other guys with flyer in sort of a bit the same style as this one and they probably offer higher quality visually , so basically this is pushing quality control teams to approve your item. I believe that u need to put a bit more effort on the whole flyer visually speaking, especially when it comes to bubbles so that it looks not only ok, but really good or great … . Then , your choice of fonts is maybe a bit too siple for envato ,a s theyr are much into font and font associations … . Other guys were also right , u need to have more contrast with the main title, it must spring out much more , as this is also how u’ll have more hierarchy in the information of the document. If i were u , i would bring the whole creation up slightly too, as u have a big free space on top and really small one in the back, which basically seems to make it look lacking balance indeed. In fact that they may look high changes to brings but this is not so complicated and i think that if u fix, then it should be ok 
good luck buddy