Sometimes when I run the code it works, other times I get Run-Error '1004' and I don't know why? - vba7

Question

First of all I'm a beginner with VBA so I don't understand a lot. I tend to record my macros and then slightly modify them.
I get the following Error 1004 message
You can't paste this here because the Copy Area and paste area aren't the same size. Select just one cell in the paste area or an area that's the same size, and try pasting again.
Private Sub TransferExpenses_Click()
ThisWorkbook.Activate 'Transfer ExpenseImport Data over to CMiCExport Tab
Sheets("ExpenseImport").Select
Range("A1:AE1", Selection.End(xlDown)).Select
Selection.Copy
ThisWorkbook.Activate
Sheets("CMiCExport").Select
Sheets("CMiCExport").Range("A1").Select
Selection.End(xlDown).Select
ActiveCell.Offset(1, 0).Range("A1").Select
Sheets("CMiCExport").Paste
MsgBox Title:="Expenses Imported Successfully!", Prompt:="The data for your expenses was verified and transferred to the CMiCExport Tab. Please double check column C -Job & Scope- and revise the .XXDefault entries."
End Sub
I'm basically just trying to copy data from one sheet "ExpenseImport" to "CMiCExport" on the next blank row. The data will always be from column A to AE since it's mapped, but the rows will always vary depending on the amount of entries for that particular week. When I step into and run the code using the "F8" it works just fine, but when running the code using an active control, it fails. Can someone help me?

Answer 1

I think it´s because the blank cells. Try this:
Private Sub TransferExpenses_Click()
ThisWorkbook.Activate 'Transfer ExpenseImport Data over to CMiCExport Tab
Sheets("ExpenseImport").Select
Range("A1:AE1", Selection.End(xlDown)).Select
'Avoid the copy if all cells are blank
If Application.WorksheetFunction.CountBlank(Selection) = Application.WorksheetFunction.CountBlank(Selection) Then
Exit Sub
End If
Selection.Copy
ThisWorkbook.Activate
Sheets("CMiCExport").Select
Sheets("CMiCExport").Range("A1").Select
Selection.End(xlDown).Select
ActiveCell.Offset(1, 0).Range("A1").Select
Sheets("CMiCExport").Paste
MsgBox Title:="Expenses Imported Successfully!", Prompt:="The data for your expenses was verified and transferred to the CMiCExport Tab. Please double check column C -Job & Scope- and revise the .XXDefault entries."
End Sub