Serial Port Communication - Error: port does not exist

[Lalaluye]

I'm trying to open a port using "Imports System.IO.Ports" and this function:

#Region "Manager Variables"
    'property variables
    Private _baudRate As String = String.Empty
    ' Private _parity As String = String.Empty
    Private _stopBits As String = String.Empty
    Private _dataBits As String = String.Empty
    Private _portName As String = String.Empty
    Private _transType As TransmissionType
    Private _msg As String
    Private _type As MessageType
    'global manager variables
    Private comPort As New SerialPort()
    Private write As Boolean = True
#End Region

    Public Function OpenPort() As Boolean
        Try
            'first check if the port is already open
            'if its open then close it
            If comPort.IsOpen = True Then
                comPort.Close()
            End If

            comPort.BaudRate = Integer.Parse(_baudRate)
            comPort.DataBits = Integer.Parse(_dataBits)
            comPort.StopBits = DirectCast([Enum].Parse(GetType(StopBits), _stopBits), StopBits)
            comPort.Parity = DirectCast([Enum].Parse(GetType(Parity), _parity), Parity)
            comPort.PortName = _portName

            comPort.Open()

            'display message
            _type = MessageType.Normal
            _msg = "Port opened at " + DateTime.Now + "" + Environment.NewLine + ""
            MsgBox(_type, _msg)
            'return true
            Return True
        Catch ex As Exception
            MsgBox(MessageType.[Error], ex.Message)
            Return False
        End Try
    End Function

My values are set as follows:
comPort.BaudRate = 9600
comPort.DataBits = 8
comPort.StopBits = 1
comPort.PortName = COM18
comport.Parity = "None"

But I get jumped to "Catch ex As Exception" with an error message - COM18 does not exist at line "comport.Open()"

I'm pretty sure it exists as it shows up on my device manager.

Edit: I used the System.IO.Ports.SerialPort.GetPortNames() to see all the available ports and COM18 is not listed. But it shows up on the device manager. Is it not a serial port?