I've a problem with a complicated SVG image.
It works on Chrome and Firefox, but there is no way to convert it into a PNG image even using an online tool or GIMP and also with Inkscape.
I'm not sure where the problem is. Maybe because is it an image built with two other SVG images embedded.
Here is the SVG file.
To reproduce the problem: open the SVG file linked with a browser: it works.
Open it with GIMP and the image is empty.
An easier example with the same problem:
<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg viewBox="0 0 10 10" xmlns="http://www.w3.org/2000/svg">
<!-- Some graphical objects to use -->
<defs>
<svg id="pippo" viewBox="0 0 10 10" >
<circle id="myCircle" cx="5" cy="5" r="5" />
</svg>
<linearGradient id="myGradient" gradientTransform="rotate(90)">
<stop offset="20%" stop-color="gold" />
<stop offset="90%" stop-color="red" />
</linearGradient>
</defs>
<!-- Using my graphical objects -->
<rect height="100%" width="100%" fill="#fc0" />
<use x="0" y="0" href="#pippo" fill="url('#myGradient')" />
</svg>