To solve this problem, make sure you upload 1024 x 1024 png files for IOS icon and also Default icon. Do not use jpg icons. Also if this fails to solve your problem, make sure you delete all icons in your construct2 editor. You can do this in the Project browser on the right of the Construct2 editor. Just scroll down to the Icon folder and delete all the icons there. That will force cocoon.io to regenerate all the icons.