ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI=1/C4H6N2O2/c1-2-8-4(7)3-6-5/h3H,2H2,1H3/file?format=sdf&get3d=True  -- InChI=1/C4H6N2O2/c1-2-8-4(7)3-6-5/h3H,2H2,1H3 could not be loaded.