Digital Signature Stops Macro

I have a new problem with the same code so have started a new thread. (Hope this is O.K. moderators?)

My code is conditionally opening spreadsheets in a folder, pulling information from certain cells and putting them in a master spreadsheet.

When it comes across a spreadsheet that has been digitally signed I get the error message-

Copy method of range class failed

Option Explicit

Sub nicksmacro()

  Dim C As Long
  Dim Cell As Range
  Dim DstRng As Range
  Dim MyDir, FN As String
  Dim LR As Long
  Dim SrcRng As Range
  
    Application.ScreenUpdating = False
       
   'Runtime
    MyDir = "\\C:\Test Folder\"
    
    Set DstRng = ThisWorkbook.Sheets("Sheet1").Range("A2")
    Set DstRng = DstRng.Resize(RowSize:=DstRng.Parent.UsedRange.Rows.Count)
    
      FN = Dir(MyDir & "*Summary*.xls")
    
      Do While FN <> ""
        If FN <> ThisWorkbook.Name Then
            With Workbooks.Open(MyDir & FN)
                Set SrcRng = .Sheets("Sheet1").Range("E3,c22,c23,c24,c25")
                  For Each Cell In SrcRng.Cells
                    Cell.Copy DstRng.Offset(LR, C)
                    C = C + 1
                  Next Cell
                .Close False
                C = 0
                LR = LR + 1
            End With
        End If
        FN = Dir()
      Loop
      
    Application.ScreenUpdating = True
End Sub

The debugger points at this line:

Cell.Copy DstRng.Offset(LR, C)

Is there a way to stop this happening?

If you follow the loop back, they increment the row count so the copied cells are pasted to the new spread sheet sequentially.

I really need to know why it stops working when it is trying to extract information from cells in a digitally signed file.