Data back NULL in OPC UA client with VB.net - opc-ua

Question

im trying to connect to a S7 1500 PLC with an OPC UA client with the Visual Studio using VB.net.
The project need to be auto, so i have an Excel that have the names of the variables that i will read with the OPC connection.
The problem is that when i try to read a single node it works and give me back the value correctly, but when i tried to do it with an array to save the data (for later introduccing it in an SQL Server) i gave me back the value NULL, i have tried to convert using CType or other but it still fails.
here Is the code:
The variable Arr_Celdas contanins the names of the vars for the string. The var Rwcnt is a function that reads the number of rows in the Excel(number of variables). And the Var Filas is for the Fors
Dim Client_OPC As New OpcClient("opc.tcp://10.1.0.128:4840") 'Conexión
Dim Lectura_OPC(Fila) As String 'Array con los nombres de las variables para la lectura de valores OPC
Dim Valor_Nodo_OPC(Rwcnt) As OpcValue 'Variable con el valor del nodo OPC
Client_OPC.Connect() 'Conexión al servidor
If Err.Number = 0 Then 'Rutina de espera antes del siguiente paso y rutina de error
Console.WriteLine("Cliente OPC conectado")
System.Threading.Thread.Sleep(2000)
Else
Dim ErrorDesc As String = Err.Description & "(" & Err.Number & ")"
Console.WriteLine(ErrorDesc)
Client_OPC.Disconnect()
Exit Sub
End If
Dim Lectura_OPC_1 As String = """ns = 3;s=""Registros_procesados"".""Registros_ATV_Izda""."""
Dim Lectura_OPC_2(Fila) As String
For Fila = 1 To Rwcnt
Lectura_OPC_2(Fila) = Arr_Celdas(Fila) + """"
Lectura_OPC(Fila) = Lectura_OPC_1 + Lectura_OPC_2(Fila) + """"
Next
'Console.WriteLine(Lectura_OPC(11))
Do While (True) 'Bucle cada 100 ms
'Dim Prueba As OpcValue = Client_OPC.ReadNode("ns=3;s=""Registros_procesados"".""Registros_ATV_Izda"".""Encoder frequency""") 'Valor encoder y lectura del nodo correspondiente
For Fila = 1 To Rwcnt
Valor_Nodo_OPC(Fila) = CType(Client_OPC.ReadNode(Lectura_OPC(Fila)), OpcValue)
Next
If Err.Number = 0 Then 'Rutina de espera antes del siguiente paso y rutina de error
Console.WriteLine("Obteniendo valores")
'System.Threading.Thread.Sleep(2000)
Else
Dim ErrorDesc As String = Err.Description & "(" & Err.Number & ")"
Console.WriteLine(ErrorDesc)
Client_OPC.Disconnect()
Exit Sub
End If
Console.WriteLine(Valor_Nodo_OPC(11))
THANKS AND HOPE U CAN HELP ME :)