Hello Jason,
I have taken a look at your image file and there is nothing wrong with it.
All image files are squared off like this.
The purpose of the "transparent" corners is to provide an overlay that has no coloring around your button ... so that the background of whatever you have placed it on will show through it
So if you place it on a black background, you will see black all the way around the button, tight to the edges. If it is over white, white tight to the edges like in the png that you attached to your project (open it in a new tab in your web browser). You do not see clear corners ... just white
Please, if you need any help or have any questions ... let me know. Do not waste $ on Freelancer that promises to remove the transparent corners ... you can color them, but that is not what you want to do and definitely not worth $! You can do that yourself.
I look forward to hearing from you.