Error on unable to set FormulaArray Property

Range("J29").FormulaArray = _
            "=IFERROR(SUMPRODUCT((RIGHT('Actual Order Intake'!R4C16:R1500C16,3)=RIGHT(MainPage!R29C3,3))*(RIGHT('Actual Order Intake'!R4C2:R1500C2,3)=MainPage!R29C4)*('Actual Order Intake'!R4C3:R1500C3=RIGHT(MainPage!R5C10,3))*(IF(ISERROR(LEFT('Actual Order Intake'!R4C12:R1500C12,2)+0),0,LEFT('Actual Order Intake'!R4C12:R1500C12,2)+0)=R4C6)*('Actual Order Intake'!R4C10:R1500C10)), 0)"

Why is there error on this whole line? The error says that Run-time error '1004': Unable to set the FormulaArray property of the Range class

Dim FormulaPart1 As String
Dim FormulaPart2 As String

FormulaPart1 = "=IFERROR(SUMPRODUCT((RIGHT('Actual Order Intake'!R4C16:R1500C16,3)=RIGHT(MainPage!R29C3,3))*(RIGHT('Actual Order Intake'!R4C2:R1500C2,3)=MainPage!R29C4)*('Actual Order Intake'!R4C3:R1500C3=RIGHT(MainPage!R5C10,3))*,""""," & _
            "X_X_X())"
FormulaPart2 = "(IF(ISERROR(LEFT('Actual Order Intake'!R4C12:R1500C12,2)+0),0,LEFT('Actual Order Intake'!R4C12:R1500C12,2)+0)=R4C6)*('Actual Order Intake'!R4C10:R1500C10)),0)"

With shMainPage.Range("J29")
      .FormulaArray = FormulaPart1
      .Replace "X_X_X()", FormulaPart2
End With

I have search for some clues on the internet. Seems like I found that method, but it could not get it working. The error highlight at line ".FormulaArray = FormulaPart1"