Open Active Workbook - vba

Question

I have VBA code that should pick up the active workbook (and use the data to open a Word Document and leave the mail merged document open ready for review/saving).
It worked once but now it isn't picking up the open spreadsheet. It opens a 'Select Table' window of which the only option is the XLSTART.xls spreadsheet with no data.
How do I pick up the active workbook?
Sub Mailmerge()
Dim wd As Object
Dim wdocSource As Object
Application.DisplayAlerts = False
' Word constants
Const wdFormLetters = 0, wdOpenFormatAuto = 0
Const wdSendToNewDocument = 0, wdDefaultFirstRecord = 1, wdDefaultLastRecord = -16
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("File Name for Mail Merge doc, this bit works when not redacted!")
strWorkbookName = ThisWorkbook.Path & "\" & ThisWorkbook.Name
wdocSource.Mailmerge.MainDocumentType = wdFormLetters
wdocSource.Mailmerge.OpenDataSource _
Name:=strWorkbookName, _
AddToRecentFiles:=True, _
Revert:=False, _
Format:=wdOpenFormatAuto, _
Connection:="Data Source=" & strWorkbookName & ";Mode=Read", _
SQLStatement:="SELECT * FROM `Sheet2$`"
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