In what scenarios does mass spectrometry and elemental analysis fail?

Ive been trying to determine the structure of a complex from its IR, H NMR, elemental analysis, and mass spectrum but im getting conflicting structures (ie. a structure supported by H NMR and IR), but not elemental analysis and MS. Is there a case where mass spectrometry and/or elemental analysis would fail? maybe involving higher nuclearity metal complexes (eg. binuclear)