Once I formatted it to remove the HTML (below) I suspect it's this line
strWorkbookName = ThisWorkbook.Path & "\" & ThisWorkbook.Name & "C:\Users\stephenc1\OneDrive - Carnival Corporation\Joiners_Docs\Seabourn Recruitment Tracker.xlsm"
Sub RunMerge()
Dim wd As Object
Dim wdocSource As Object
Dim strWorkbookName As String
On Error Resume Next
Set wd = GetObject(, "Word.Application")
If wd Is Nothing Then
Set wd = CreateObject("Word.Application")
End If
On Error GoTo 0
Set wdocSource = wd.Documents.Open("C:\Users\stephenc1\OneDrive - Carnival Corporation\Joiners_Docs\HR_Email_One_Docs\Visa Mail Merge.docx")
strWorkbookName = ThisWorkbook.Path & "\" & ThisWorkbook.Name & "C:\Users\stephenc1\OneDrive - Carnival Corporation\Joiners_Docs\Seabourn Recruitment Tracker.xlsm"
wdocSource.MailMerge.MainDocumentType = wdFormLetters
wdocSource.MailMerge.OpenDataSource _
Name:=strWorkbookName, _
AddToRecentFiles:=False, _
Revert:=False, _
Format:=wdOpenFormatAuto, _
Connection:="Data Source=" & strWorkbookName & ";Mode=Read", _
SQLStatement:="SELECT * FROM `Visa$`"
With wdocSource.MailMerge
.Destination = wdSendToNewDocument
.SuppressBlankLines = True
With .DataSource
.FirstRecord = wdDefaultFirstRecord
.LastRecord = wdDefaultLastRecord
End With
.Execute Pause:=False
End With
wd.Visible = True
wdocSource.Close SaveChanges:=False
Set wdocSource = Nothing
Set wd = Nothing
End Sub