attribute key not found error while processing the cube in SSAS

Attribute Key Not found Error occurs in SSAS due to the following reasons :

 

1. Dimensions processed after measure groups
2. Null values / references in Keys
3. Please check for the Null values in Interrelated dimensions.

(For Ex : You might have a dimension table employees, employees relates to table sub department, subdepartment relates to table department.

If by chance there exists a Null value in the mapping between subdepartment and department you will get this error).