For some reason the driver is not creating what is referred to a DLL. This is what allows all of the communications.
In the Solution Explorer, exapand down the AdvancedHMIDrivers project, then expand down the Modbus folder. Right clock ModbusRTU.vb and select View Code
Go down to line 199 and put a break point by clicking in the left margin until you get a red dot
Run the application and it should stop at that break point. When it does press F10 and see if it steps through this code:
If MyDLLInstance >= DLL.Count Then
Dim NewDLL As New ModbusRTUDataLinkLayer(m_PortName)
NewDLL.BaudRate = m_BaudRate
NewDLL.DataBits = m_DataBits
NewDLL.Parity = m_Parity
NewDLL.StopBits = m_StopBits
DLL.Add(NewDLL)
End If