How do I debug a "silent" Process failure?

I am printing PDF files like this. It works fine for most of my printers:

Public Sub PrintFile(ByVal uPath As String, ByVal uPrinter As String)

    Dim psi As New ProcessStartInfo
    psi.WindowStyle = ProcessWindowStyle.Normal
    psi.Verb = "printto"
    psi.Arguments = uPrinter
    psi.CreateNoWindow = False
    psi.FileName = uPath

    Dim nProc As New Process
    nProc.StartInfo = psi
    nProc.Start()

    If nProc Is Nothing Then
        MsgBox("failed!!!")
    End If

    DoSleep(3000)

    Do While Not modEnvironment.IsPrinterQueueEmpty()
        DoSleep(2000)
    Loop

    Try
        nProc.CloseMainWindow()
    Catch ex As Exception
         Debug.Assert(False)
    End Try
    nProc.Close()

End Sub

This works fine for some printers.

For one printer, it does not work. The name I have given it is

"Canon MB2700 series Printer Wifi"

As one can guess, it's a Wifi printer. But I am not aware that Wifi printers have to be treated differently than locally connected printers.

There is no obvious error thrown or different process ExitCode, it just does not print.

I have compared the printer names again and again, I do not see any obvious spelling mistake or so.

That is why I would like to ask how I could debug what goes wrong in this case.

Thank you!