Я немного изменил ваш код, и я почти уверен, что ваш код не может работать.Вы правильно скопировали из рабочей книги, но затем закрыли ее и попытались вставить в текущую рабочую книгу.Если вы закроете книгу во время копирования, вставлять нечего.
Option Explicit
Sub PopulateUploaderFunds()
Dim uploadfile As String 'not variant
Dim uploader As Workbook
Dim CurrentBook As Workbook
MsgBox ("Please select uploader file to be reviewed")
uploadfile = Application.FileDialog(msoFileDialogFilePicker)
With Application.FileDialog(msoFileDialogFilePicker)
.InitialFileName = "C:\" 'here you change the path
.AllowMultiSelect = False
.Filters.Add "CSV", "*.csv"
If .Show <> -1 Then Exit Sub ' if Cancel is pressed
uploadfile = .SelectedItems(1)
End With
Set CurrentBook = ThisWorkbook 'ActiveWorkbook would throw errors, ThisWorkbooks refers to the workbook which contains the code
Application.ScreenUpdating = False
Application.DisplayAlerts = False
Set uploader = Workbooks.Open(uploadfile, ReadOnly:=True) 'you can directly set the uploader workbook like this
With uploader
.Sheets("MySheet").UsedRange.Copy CurrentBook.Sheets("Sheet1").Range("A1") 'change MySheet for the name of your working sheet
Application.CutCopyMode = False
.Close SaveChanges:=False
End With
Application.ScreenUpdating = True
End Sub