# OpcClient.NotificationFailed Event

<dl class="api-definition">
<dt>Type</dt>
<dd><a href="./">OpcClient</a></dd>
<dt>Namespace</dt>
<dd><a href="../namespaces/opc.uafx.client">Opc.UaFx.Client</a></dd>
<dt>Assembly</dt>
<dd>Opc.UaFx.Advanced.dll</dd>
<dt>Package</dt>
<dd>Opc.UaFx.Advanced v2.59.0</dd>
<dt>Members</dt>
<dd><a href="./members">OpcClient Members</a></dd>
<dt>Also in</dt>
<dd>Opc.UaFx.Client</dd>
</dl>

<span class="api-meta">since v2.57</span>

Occurs when a notification message from the server connected to failed to be received, so that its data changes and events do not reach the monitored items.

<div class="api-signature" data-lang="csharp">

```csharp
public event OpcNotificationFailedEventHandler NotificationFailed
```

</div>

<div class="api-signature" data-lang="vbnet">

```vbnet
Public Event NotificationFailed As OpcNotificationFailedEventHandler
```

</div>

**Event type**

[OpcNotificationFailedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationfailedeventhandler/)

**Remarks**

A response which cannot be processed does not state the subscription of its message, so this event occurs for it with no [Subscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationfailedeventargs/members#subscription). The session requests the message again from the server until the server no longer holds it; once it fails again, the failure is reported with its subscription, once for each message however often it fails, and once more with [BadMessageNotAvailable](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badmessagenotavailable) when the message is lost. Such a failure only occurs here if it is not handled by the [NotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#notificationfailed) handler of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).