SAP- Connect to SAP from using .net connectors - error calling SAP query

Question

I have the below code , VB code trying to connect to SAP

getting the below error :

‘destination FSD failed when calling RFC_METADATA_GET’ ‘Exception thrown: 'SAP.Middleware.Connector.RfcCommunicationException' in sapnco.dll’

Code:

Private Shared Function Invoke(ByVal destination As RfcDestination, ByVal table As String, ByVal fields As List(Of SAPFieldItem), ByVal options As List(Of SAPFieldItem))

    Try


        '04052022
        Dim func As IRfcFunction = destination.Repository.CreateFunction("RFC_GET_CUST")  ' QUE_DOTNET__01   'RFC_GET_CUST

        'set fields
        If fields IsNot Nothing Then
            Dim fs As IRfcTable = func.GetTable("FIELDS")
            For i As Integer = 0 To fields.Count - 1
                fs.Append()
                fs.CurrentIndex = i
                fs.SetValue("FIELDNAME", fields(i).FieldId)
            Next
        End If

        'set options
        If options IsNot Nothing Then
            Dim opts As IRfcTable = func.GetTable("OPTIONS")
            For i As Integer = 0 To options.Count - 1
                opts.Append()
                opts.CurrentIndex = i
                opts.SetValue("TEXT", If(i > 0, " AND ", "") + options(i).makeWhere)
            Next
        End If

        func.SetValue("QUERY_TABLE", SAPFieldItem.escape(table))

        func.Invoke(destination)

        Dim result As New List(Of Dictionary(Of String, String))

        Dim index As Integer = 0
        Dim struct As IRfcTable = func.GetTable("FIELDS")
        Dim columns As New Dictionary(Of String, Integer)

        For i As Integer = 0 To struct.Count - 1
            struct.CurrentIndex = i
            columns.Add(struct.GetString("FIELDNAME"), struct.GetInt("LENGTH"))
        Next

        Dim data As IRfcTable = func.GetTable("DATA")
        For i As Long = 0 To data.Count - 1
            data.CurrentIndex = i
            Dim line = data.GetString("WA")

            Dim row As New Dictionary(Of String, String)
            Dim position As Integer = 0
            For Each c In columns
                If position + c.Value <= line.Length Then
                    row.Add(c.Key, line.Substring(position, c.Value).Trim)
                ElseIf position <= line.Length Then
                    row.Add(c.Key, line.Substring(position).Trim)
                Else
                    row.Add(c.Key, String.Empty)
                End If
                position += c.Value
            Next
            result.Add(row)
        Next

        Return result
    Catch ex As Exception
        Console.WriteLine(ex.Message)
    End Try
End Function