User blog:EvilCanadaball/Can't upload screenshot

I've been trying to upload a cropped screenshot of a drawing made in an app from my photos onto my profile page, but every time it says that there is a "permission error." I've read the terms of use on the app and I'm not violating anything, and I checked to make sure the image will fit. What exactly is the error? Who do I need permission from? Isn't this technically my property?

I need advice.