Your epsfile is a CMYKA file. This is not supported by Ghostscript. You can read the image with transparency if you specify the colorspace as sRGB before reading the image:
MagickReadSettings settings = new MagickReadSettings(); settings.ColorSpace = ColorSpace.sRGB; using (MagickImage magickImage1 = new MagickImage(sourceFilePath, settings)) { magickImage1.Write(@"C:\testPNG.png"); }