The {2} expression for the {0} '{1}' contains a nested aggregate that does not specify a scope. In a tablix cell that belongs ...

The {2} expression for the {0} '{1}' contains a nested aggregate that does not specify a scope. In a tablix cell that belongs to both row and column groups, or on a data point that belongs to both series and category groups, when the outer aggregate specifies a group scope,  nested aggregates must specify a scope.