We have defined all the variables for the materials. However, when I attempt to use Material Matchcode object MAT1, I get the response "No possible entries found". Why?

Matchcode i.d. "B", "Material by bill of material" has a selection condition for field STLNR NE ' '. STLNR is the BOM number associated with a material in table MAST. Hence the message - "no possible entries..." pops up if there are no bills of materials associated with your material numbers. You get the matchcodes as long as the material referred by you has BOM number associated with it.