I created an image of the outline of a feature I want to add to the silkscreen layer. I saved it as a PNG with transparency and uploaded it. It appeared on the silkscreen layer with the transparent parts as solid and the solid parts as transparent.
I created a monochrome bitmap; black features on a white background. I uploaded that with the same result. The white parts are shown as silkscreen and the black parts (that I want to see) are not shown.
I tried other file formats with the same result.
I inverted the bitmap. The parts I want to see are white and the background is black. I uploaded that file and still got the same result; The outline I want to appear is not shown on the silkscreen layer and the background is a great lump of solid aqua.
I tried the same thing a few days ago and it worked fine. It seems that this new “feature” is recent.