Diagnosis
This sales area has either not been designed (i.e. noentry in TVTA), or it refers to another sales area for customers(customer division/customer distribution channel in detail screenTVTA).In other words, the customer master data of the sales areaspecified corresponds to that of the reference area and only for thelatter is the customer master data and the hierarchy maintenanceallowed.

Procedure
You can maintain common master data in Customizing, using menu pathOrganization -> Assignments -> Logistics -> SD.