In spite of several attempts at synthesizing MnNb2S4, a II− −III2−VI4 semiconducting material with potentially interesting magnetic properties, MnNb3S6, a closely related compound was always prepared as the majority phase. The material was characterized using X-ray Powder Diffraction data. The refinement of the structure of this material carried out by the Rietveld Method produced results consistent with a previously reported study. The unsuccessful attempts of producing MnNb2S4 raise doubts about the existence of this compound.