Button not displaying on Mac (C# plugin)

Grasshopper Developer
,
1

Why does some elements in my C# plugin no show up on mac os?
As seen below, on the toolbar beside the sketch button
on Windows, it shows up fine:
image
on Mac, button icon is empty:

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I’m creating the button like this:

ToolStripItemCollection items = ((ToolStrip)(Instances.DocumentEditor).Controls[0].Controls[1]).Items;
items.Add(new ToolStripButton("Create Snippet", Properties.Resources.SnippetBuilder, (s, e) => Snippet.Save(canvas.Document))
{
    Name = "Melanoplus_Snippet",
    DisplayStyle = ToolStripItemDisplayStyle.Image,
});