SAP Message WRF_REF020 - &4 Material/plant combinations found are not suitable references

Diagnosis
Although the system has found several material/plant combinations, thesystem could not assign any of them as a reference.

System Response
Due to several possible reasons, no combination is a suitable reference.One reason might be, for example, that the material has the wrongmaterial category. If this message occurred during automatic assignmentof references, then the system could not create a reference assignmentfor material &V1& and plant &V2&.