S_GlowEdges need help?

Hi, I work in Sony Vegas Pro 16.

I have a problem with S_GlowEdges, I put S_GlowEdges on a source, a png image. But if I change the settings of the S_GlowEdges a black box appears behind the png image. This black box won’t go away and does not go away with chroma key because in the png image I have black colors and with Alpha Channel set to Premultipied/Premultipied (dirty) it also wont dissappear.

Can somebody help me?