ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI%3DInChI%3D1S/C4H6O2/c1-3-6-4%282%295/h3H%2C1H2%2C2H3/file?format=sdf&get3d=True  -- InChI%3DInChI%3D1S/C4H6O2/c1-3-6-4%282%295/h3H%2C1H2%2C2H3 could not be loaded.