I think the problem can be in the fact that for the subscribe, you are *not* providing user authentication. 

In the call to  , you pass in just the serverUrl, not the endpoint descriptor with the user name identity.

Best way would be to create the UAEndpointDescriptor just once, with the user identity, assign it to a variable, and then use it for both Read and Subscribe operations.

Best regards

Yes, I'm able to read and read valid data with ReadMultiple. But when I try to subscribe to the same node the SubscribeMultipleMonitoredItems returns the subscription id, but the EasyUADataChangeNotificationEventArgs in callback has Succeeded=false and the Exception="OpcLabs.EasyOpc.UA.UAServiceException: OPC UA service result - {BadNotReadable}. The access level does not allow reading or subscribing to the Node."

Here is the code:

EasyUAClient.SharedParameters.EngineParameters.CertificateAcceptancePolicy = new OpcLabs.EasyOpc.UA.Engine.UACertificateAcceptancePolicy()
{
    AcceptAnyCertificate = true
};
var client = new EasyUAClient();
string serverUrl = "opc.tcp://192.168.214.1:4840";
var nodeId = "ns=2;s=/Channel/GeometricAxis/aaIwCorr[1]";

// ===== READ
var readRequests = new List<UAReadArguments>
{
    new(new UAEndpointDescriptor(serverUrl).WithUserNameIdentity("user", "password"), new UANodeDescriptor(nodeId)),
};

var values = client.ReadMultiple([.. readRequests]);

var monitoredItems = new List<EasyUAMonitoredItemArguments>()
{
    new EasyUAMonitoredItemArguments(Callback, null, serverUrl, nodeId, 1000)
};

// ===== SUBSCRIBE
var subResults = client.SubscribeMultipleMonitoredItems([.. monitoredItems]);
static void Callback(object sender, EasyUADataChangeNotificationEventArgs e)
{

}
 

Hello.

Are you saying that you were actually able to read the node, but get this error when trying to subscribe to the very same node?

Regards
 

I enabled "AcceptAnyCertificate", but it seems I still cannot subscribe to a node. When I try to subscribe with "SubscribeMultipleMonitoredItems" I get the following error "OPC UA service result - {BadNotReadable}. The access level does not allow reading or subscribing to the Node.". Does this mean that I do need certificate or do I need to enable/allow something on UA Server?

EasyUAClient.SharedParameters.EngineParameters.CertificateAcceptancePolicy = new OpcLabs.EasyOpc.UA.Engine.UACertificateAcceptancePolicy()
{
    AcceptAnyCertificate = true
};
var opcClient = new EasyUAClient();