VBA Error Run-Time 91 - object variable or with block variable not set (Code included)

[LNG2013]

When I am trying to run the following code I am getting an error of:
Run-Time error '91':

Object variable or With block variable not set

Sub CreatePivot()


Dim nr As Range
Dim pt As PivotTable
Dim ws As Worksheet
Dim LastRow As Long




For Each ws In Worksheets
    Select Case ws.Name
        Case "Data0", "Data1", "Data2", "Data3", "Data4", "Data5"
 
            With ws


     LastRow = .Range("N" & .Rows.Count).End(xlUp).Row
          nr = ws.Range("A2" & ":O" & LastRow)
         
         
        ActiveWorkbook.PivotCaches.Create(SourceType:=xlDatabase, SourceData:= _
            ws.Name & nr, Version:=3) _
            .CreatePivotTable TableDestination:=ws.Name & "A" & LastRow + 10, _
            TableName:="PivotTable4", DefaultVersion:=xlPivotTableVersion14
        Set pt = ws.PivotTables("PivotTable4")
        pt.AddDataField pt.PivotFields("Code"), "Sum of Code", xlSum
        With pt.PivotFields("SessionDate")
            .Orientation = xlRowField
            .Position = 1
        End With
       
        With pt.PivotFields("Session")
            .Orientation = xlRowField
            .Position = 2
        End With
       
        With pt.PivotFields("Probe#")
            .Orientation = xlRowField
            .Position = 3
        End With
       
     
    End With

        Case Else
            'Do Nothing
    End Select
Next ws

End Sub

 

[MARK858]

Try

Set nr = ws.Range("A2:O" & LastRow)

but looking at the rest of your code you have other issues after that line