settlement error with correct rules

in my settlement profile Z1, I define default object type: MAT, allocation structure Z2. settlement optional: material

in Z2 setting, I define assignment line 010, cost element group: ZCO_001, in ZCO_001 i include all cost element

in settlement cost element, I define receiver category: CTR, by cost element

I try to define receiver category: MAT, by cost element

I try to settle to Material, in my order, I already find order settlement rule: MAT, material 1200020 full, settlement parameter; allocation structure: Z2

but I hit below error using KO88 to settle my order to MAT

Account type M is not defined for document type SA

Message no. F5243

how to resolve?