VBA code error for assigning a value in "For Each"

for sure this

Set pvtTable = ActiveSheet.PivotTables("PivotTable1").PivotFields("END DATE")
    For Each pvtFld In pvtTable.PivotFields

is wrong as you try to assign a PivotField object to PivotTable variable.

proper code shall be:

Set pvtTable = ActiveSheet.PivotTables("PivotTable1")
    For Each pvtFld In pvtTable.PivotFields

I don't want to produce dummy data to test your issue but may be (?) the problem is with data stored in enddate type? May be it's not date type?

You may test it that way:

Dim pvtFld As PivotField
Dim pvtTable As PivotTable
Set pvtTable = ActiveSheet.PivotTables("PivotTable1")
    For Each pvtFld In pvtTable.PivotFields
      If pvtFld.Name Like "*END DATE*" Then
        Select Case pvtFld.DataType 
          Case Is = xlText 
            MsgBox "The field contains text data" 
          Case Is = xlNumber 
            MsgBox "The field contains numeric data" 
          Case Is = xlDate 
            MsgBox "The field contains date data" 
        End Select 
      End If
    Next pvtFld
Set pvtTable = Nothing

But general comment by gijsmo that with sample file we could test it is 100% valid