ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI%3DInChI%3D1S/C4H6N2/c1-4-2-5-6-3-4/h2-3H%2C1H3%2C%28H%2C5%2C6%29/file?format=sdf&get3d=True -- InChI%3DInChI%3D1S/C4H6N2/c1-4-2-5-6-3-4/h2-3H%2C1H3%2C%28H%2C5%2C6%29 could not be loaded.