According to the Mozilla Developer Network
Starting with Gecko 2.0 (Firefox 4 / Thunderbird 3.3 / SeaMonkey 2.1),
Gecko also supports the SVG image format for cursors. However, the SVG
image must contain a length-valued (not percentage-valued) height and
width on its root SVG node. JavaScript, CSS animation, and declarative
SMIL inside an SVG image are ignored; you can't use SVG to create an
animated cursor, for example.
Therefore, you should explicitly declare the height and width in your .svg file.
The .svg you provided has no dimensions declared as you can see:
<svg xmlns="http://www.w3.org/2000/svg" id="Capa_1" viewBox="0 0 320.995 320.995" x="0px" y="0px" height="200" xmlns:xml="http://www.w3.org/XML/1998/namespace" xml:space="preserve" viewbox="0 0 320.995 320.995" version="1.1">
If you add the width and height attributes, you should be fine.
Just make sure you don't declare the dimensions with percentages