runtime error 1004 : excel VBA - excel

Question

I keep getting runtime error 1004, on the following line:
originBook.Sheets(1).Range(Cells(1, 1), Cells(lastRow, lastCol)).Copy
Here's the full code
Sub Obtain_Source()
Application.DisplayAlerts = False
Dim theOrigin, theString, newCol As String
Dim lastRow, lastCol As Long
Dim theRange As Range
Dim originBook, originBookBackup, macroBook As Workbook
Dim originOpen As Boolean
originOpen = False
Set macroBook = Workbooks("FY_Macro_Testt (DYNAMIC).xlsm")
theOrigin = Application.GetOpenFilename(fileFilter:="Excel Files (*.xls; *.xlsm; *.xlsx), *.xls' *.xlsm' *.xlsx", _
Title:="Fiscal Year Selection: Select Only One", ButtonText:="Open", MultiSelect:=False)
If TypeName(theOrigin) = "Boolean" Then
MsgBox "Don't just stand there. Do something." & vbNewLine & _
"Quit hitting CANCEL. >.< ", vbExclamation, "WARNING. CHOKING HAZARD."
Else
originOpen = True
Set originBook = Workbooks.Open(theOrigin)
lastRow = Range("A65536").End(xlUp).Row
lastCol = Range("XFD1").End(xlToLeft).Column
lastCol = originBook.Sheets(1).Cells(1, Columns.Count).End(xlToLeft).Column
originBook.Sheets(2).Visible = False
originBook.Sheets(3).Visible = False
originBook.Sheets(1).Range(Cells(1, 1), Cells(lastRow, lastCol)).Copy
macroBook.Sheets(1).Cells(6, 1).PasteSpecial
i = 1000
Do While 1000 <= 20000
j = i - 999
If originBook.Sheets(1).Cells(i, 1).Value <> vbNullString Or _
originBook.Sheets(1).Cells(i, 1).Value <> "" Then
originBook.Sheets(1).Range(Cells(j, 1), Cells(i - 1, lastCol)).Copy
macroBook.Sheets(1).Cells(j + 5, 1).PasteSpecial
End If
i = i + 1000
Loop
originBook.Sheets(2).Visible = True
originBook.Sheets(3).Visible = True
End If
If originOpen = True Then
originBook.Close
End If
End Sub
which one should I change?

Answer 1

Your error will almost certainly be because you are using
originBook.Sheets(1).Range(Cells(1, 1), Cells(lastRow, lastCol)).Copy
instead of, as #ShaiRado pointed out,
originBook.Sheets(1).Range(originBook.Sheets(1).Cells(1, 1), _
originBook.Sheets(1).Cells(lastRow, lastCol)).Copy
When they are not fully qualified, Cells references refer to cells on the ActiveSheet. Excel is therefore having to try to copy all the cells on Sheets(1) that lie in the area between two cells on the ActiveSheet. It's equivalent to saying "choose all the houses in Los Angeles that lie in the area between the intersection of E 79th St and 1st Avenue and the intersection of E 86th St and York Ave New York". (Not living in the USA, I hope that analogy makes sense.)