FA kills your .png's because the max file size is 1280x1280, and with your image being 1280 pixels wide I'm going to assume the original was bigger than that so FA had to resize the pic and well, transparency was lost in the process. So hey, you got two options to fix it, one is to go around the limitation by just updating the image file of this upload as updated image files don't get scaled down, ooor you could just completely delete and reupload this one after first downscaling the image yourself.

Oh hey nice, thanks.