Here is the whole code. THE datafields from the mailmerge code works fine for the EmailTo field, just not ReplyRecipients

The code is a merge of 2 macros I have used in the past, but seems to work ok, except for this function.

Sub PDF_Save_and_Email_FINAL()

Application.ScreenUpdating = False
Dim StrFolder As String, DocName As String, PDFFile As String, MainDoc As Document, i As Long, j As Long, EmailTo As String, EmailSubject As String, PDFUpload As String










Const StrNoChr As String = """*./\:?|"
Set MainDoc = ActiveDocument


With MainDoc
  StrFolder = .Path & "\"
  DocName = InputBox("DocumentName")
  EmailSubject = DocName
     
     
  With .MailMerge
    .Destination = wdSendToNewDocument
    .SuppressBlankLines = True
    
    On Error Resume Next
    For i = 1 To .DataSource.RecordCount
      With .DataSource
        .FirstRecord = i
        .LastRecord = i
        .ActiveRecord = i
        If Trim(.DataFields("LastName")) = "" Then Exit For
        'below line '
        
        'StrFolder = .DataFields("Folder") & "\"
        PDFFile = .DataFields("FirstName") & " " & .DataFields("LastName") & " - " & DocName
        EmailTo = .DataFields("StudentNumber")
        
        
      End With
      .Execute Pause:=False
      If Err.Number = 5631 Then
        Err.Clear
        GoTo NextRecord
      End If
      For j = 1 To Len(StrNoChr)
        PDFFile = Replace(PDFFile, Mid(StrNoChr, j, 1), "_")
      Next
      PDFFile = Trim(PDFFile)
      With ActiveDocument
        'Add the name to the footer
        '.Sections(1).Footers(wdHeaderFooterPrimary).Range.InsertBefore StrName
        '.SaveAs FileName:=StrFolder & StrName & ".docx", FileFormat:=wdFormatXMLDocument, AddToRecentFiles:=False
        ' and/or:
        .SaveAs FileName:=StrFolder & PDFFile & ".pdf", FileFormat:=wdFormatPDF, AddToRecentFiles:=False
        
            
        .Close SaveChanges:=False
        
        PDFUpload = StrFolder & PDFFile & ".pdf"
        
      End With
      
       
      'Create an Outlook object and new mail message
        
    Set OutlookApp = CreateObject("Outlook.Application")
    Set OutlookMail = OutlookApp.CreateItem(0)
        
    'Display email and specify To, Subject, etc
    With OutlookMail
        
     EmailTo = .DataFields("StudentNumber")
     ReplyToTeachers = .DataFields("Teacher")
     
  
        .Display
        .To = EmailTo
        .Subject = EmailSubject
        .Attachments.Add PDFUpload
        .ReplyRecipients.Add ReplyToTeachers
        
        
        If DisplayEmail = False Then
            
            .send
            
            Else
            
            '.send
            
        End If
        
    
      End With
      
      
NextRecord:
    Next i
  End With
End With
Application.ScreenUpdating = True




End Sub