ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1S/C2H4N2O6/c5-3(6)9-1-2-10-4(7)8/h1-2H2/file?format=sdf&get3d=True  -- InChI=1S/C2H4N2O6/c5-3(6)9-1-2-10-4(7)8/h1-2H2 could not be loaded.