Runtime error when merging to Microsoft Word

[theatl96]

The macro below is used to create invoices by merging a spreadsheet into Word, naming the document, and saving it as a pdf into a specified folder. This macro has worked in the past, but now I'm getting a runtime error 5941 when I try to run it.

My code is posted below with the line of code causing the issue in red. I found a solution that suggested adding Application.Templates.LoadBuildingBlocks in the line above, but it didn't solve anything.

Can anyone help? Thanks.

Sub Merge_to_pdf() '
' merge1record_at_a_time Macro
'
'
    Dim fd As FileDialog


    'Create a FileDialog object as a Folder Picker dialog box.
    Set fd = Application.FileDialog(msoFileDialogFolderPicker)
    With fd


        'Use the Show method to display the Folder Picker dialog box and return the user's action.
        'The user pressed the button.
        If .Show = -1 Then
                For Each vrtSelectedItem In .SelectedItems


                'vrtSelectedItem is aString that contains the path of each selected item.
                'You can use any file I/O functions that you want to work with this path.
                'This example displays the path in a message box.
        SelectedPath = vrtSelectedItem


        Next vrtSelectedItem


        Else
        MsgBox ("No Directory Selected.  Exiting")
        Exit Sub
        End If
    End With


    'Set the object variable to Nothing.
    Set fd = Nothing


Application.ScreenUpdating = False


MainDoc = ActiveDocument.Name
    ChangeFileOpenDirectory SelectedPath
    For i = 1 To ActiveDocument.MailMerge.DataSource.RecordCount
        With ActiveDocument.MailMerge
            .Destination = wdSendToNewDocument
            .SuppressBlankLines = True
            With .DataSource
                .FirstRecord = i
                .LastRecord = i
                .ActiveRecord = i
               [COLOR=rgb(226, 80, 65)] [B]docName = "Test Document - " & .DataFields("First_Name").Value & " " & .DataFields("Last_Name").Value & ".pdf"      ' ADDED CODE[/B][/COLOR]
            End With
            .Execute Pause:=False
    Application.ScreenUpdating = False
            
        End With
    ActiveDocument.ExportAsFixedFormat OutputFileName:=docName, _
        ExportFormat:=wdExportFormatPDF, OpenAfterExport:=False, OptimizeFor:= _
        wdExportOptimizeForPrint, Range:=wdExportAllDocument, From:=1, To:=1, _
        Item:=wdExportDocumentContent, IncludeDocProps:=True, KeepIRM:=True, _
        CreateBookmarks:=wdExportCreateNoBookmarks, DocStructureTags:=True, _
        BitmapMissingFonts:=True, UseISO19005_1:=False
    ActiveWindow.Close SaveChanges:=False
    

    Next i
Application.ScreenUpdating = True

End Sub