Macro Code for copying separate worksheets into one combined worksheet works but...

The following code works great until I figured out the last row in any of the worksheets isn't being copied.
What I have is single invoices (separate workbooks ... only one per workbook) and am selecting the folder of all the workbooks and the code copies the contents and combines all in one sheet:
Using office 2007

(had help with the code so don't understand much of the workings other than it needs to include the last row of info)

Option Explicit
Public strPath As String
Public Type SELECTINFO
    hOwner As Long
    pidlRoot As Long
    pszDisplayName As String
    lpszTitle As String
    ulFlags As Long
    lpfn As Long
    lParam As Long
    iImage As Long
End Type

Declare Function SHGetPathFromIDList Lib "shell32.dll" _
                                     Alias "SHGetPathFromIDListA" (ByVal pidl As Long, ByVal pszPath As String) As Long
Declare Function SHBrowseForFolder Lib "shell32.dll" _
                                   Alias "SHBrowseForFolderA" (lpBrowseInfo As SELECTINFO) As Long
Function SelectFolder(Optional Msg) As String
    Dim sInfo As SELECTINFO
    Dim path As String
    Dim r As Long, x As Long, pos As Integer
    sInfo.pidlRoot = 0&
    
    If IsMissing(Msg) Then
        sInfo.lpszTitle = "Select your folder."
    Else
        sInfo.lpszTitle = Msg
    End If
    
    sInfo.ulFlags = &H1
    
    x = SHBrowseForFolder(sInfo)
    
    path = Space$(512)
    r = SHGetPathFromIDList(ByVal x, ByVal path)
    If r Then
        pos = InStr(path, Chr$(0))
        SelectFolder = Left(path, pos - 1)
    Else
        SelectFolder = ""
    End If
End Function
'Merge all your excel files to a main file.
Sub MergeExcels()
    Dim path As String, ThisWB As String, lngFilecounter As Long
    Dim wbDest As Workbook, shtDest As Worksheet, ws As Worksheet
    Dim Filename As String, Wkb As Workbook
    Dim CopyRng As Range, Dest As Range
    Dim RowofCopySheet As Integer
 
    RowofCopySheet = 1 ' Row Number from where you wish to start copying
 
    ThisWB = ActiveWorkbook.Name
 
    path = SelectFolder("Select a folder containing Excel files you want to merge")
 
    Application.EnableEvents = False
    Application.ScreenUpdating = False
 
    Set shtDest = ActiveWorkbook.Sheets(1)
    Filename = Dir(path & "\*.csv", vbNormal)
    If Len(Filename) = 0 Then Exit Sub
    Do Until Filename = vbNullString
        If Not Filename = ThisWB Then
            Set Wkb = Workbooks.Open(Filename:=path & "\" & Filename)
            Set CopyRng = Wkb.Sheets(1).Range(Cells(RowofCopySheet, 1), Cells(ActiveSheet.UsedRange.Rows.Count, ActiveSheet.UsedRange.Columns.Count))
            Set Dest = shtDest.Range("A" & shtDest.UsedRange.SpecialCells(xlCellTypeLastCell).Row)
            CopyRng.Copy Dest
            Wkb.Close False
        End If
 
        Filename = Dir()
    Loop
 
    Range("A1").Select
 
    Application.EnableEvents = True
    Application.ScreenUpdating = True
 
    MsgBox "Files Merged!"
End Sub

Add the red section below

If Len(Filename) = 0 Then Exit Sub
    Do Until Filename = vbNullString
        If Not Filename = ThisWB Then
            Set Wkb = Workbooks.Open(Filename:=path & "\" & Filename)
            Set CopyRng = Wkb.Sheets(1).Range(Cells(RowofCopySheet, 1), Cells(ActiveSheet.UsedRange.Rows.Count + 1, ActiveSheet.UsedRange.Columns.Count))
            Set Dest = shtDest.Range("A" & shtDest.UsedRange.SpecialCells(xlCellTypeLastCell).Row)
            CopyRng.Copy Dest
            Wkb.Close False
        End If
 
        Filename = Dir()
    Loop