How to use correct Pivot Table VBA sub-field filter

Been trying for days to solve this problem and still no joy. I have tried to make a vba that looks at the value in cell A1 and applies it to the filter in C4 but keep getting a "Unable to get the PivotFields property of the PivotTable class" error.

This would insinuate that the code is finding the field name "Department". The filter is based off the data in the sub-field name "Department" (the field name is also "Department"

Would anyone be able to advise how to input this correctly in to the code?

Sub FilterByDepartment()
Dim WS3 As Worksheet
Dim pt As PivotTable
Dim pf As PivotField
Dim ayearweek() As Variant

' Set Worksheet meaning
Set WS3 = ThisWorkbook.Sheets("Sales Qty")

' Turn off calculation & screen updating
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = False

' Read the value from cell A1 into the ayearweek array
ReDim ayearweek(1 To 1)
ayearweek(1) = WS3.Range("A1").Value

' Refresh Master Model for article check and query
Set pt = WS3.PivotTables("Master Model")
pt.PivotCache.Refresh

' Set the Pivot table to accept multiple values
pt.CubeFields("[Department].[Department]").EnableMultiplePageItems = True

' Apply the Department filter
Set pf = pt.PivotFields("[Department].[Department]")
pf.ClearAllFilters
pf.CurrentPage = ayearweek(1)

' Tidy Up
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic

End Sub

Worked it out, the department needed a further [Department] entry and the value needed to be incorporated in to the filter entry:

'Declare Worksheet Dims'
Dim Wb1 As Workbook
Dim WS1 As Worksheet
Dim WS3 As Worksheet
Dim WS5 As Worksheet

'Set Worksheet meaning'
Set Wb1 = ThisWorkbook
Set WS3 = ThisWorkbook.Sheets("Sales Qty")

'Turn off calculation & screen updating
Application.Calculation = xlCalculationManual
Application.ScreenUpdating = False

'Refresh Master Model for article check and query
WS3.PivotTables("Master Model").PivotCache.Refresh

'Get row number of last data point
FILLY = WS3.Range("A1").Value

Range("C4").Select
ActiveSheet.PivotTables("Master Model").PivotFields("[Department].[Department].[Department]").VisibleItemsList = Array("")
ActiveSheet.PivotTables("Master Model").PivotFields("[Department].[Department].[Department]").VisibleItemsList = Array("[Department].[Department].&[" & FILLY & "]")

'Tidy Up
Range("A1").Select
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic