At startup the server logs an exception. Plugin seems to be not initialized because of that.
2023-07-18 11:11:55,898 WARN [154@MessageListener for PluginNotificationMessageListener] PluginNotificationMessageListener:62 - Notification update failed for plugin: com.example.notification.systemout
java.lang.RuntimeException: Unable to de-serialize json response. Notify result 'message' should be of type string
at com.thoughtworks.go.plugin.access.notification.v3.JsonMessageHandler3_0.toResult(JsonMessageHandler3_0.java:141)
at com.thoughtworks.go.plugin.access.notification.v3.JsonMessageHandler3_0.responseMessageForNotify(JsonMessageHandler3_0.java:87)
at com.thoughtworks.go.plugin.access.notification.NotificationExtension$2.onSuccess(NotificationExtension.java:90)
at com.thoughtworks.go.plugin.access.notification.NotificationExtension$2.onSuccess(NotificationExtension.java:82)
at com.thoughtworks.go.plugin.access.PluginRequestHelper.submitRequest(PluginRequestHelper.java:54)
at com.thoughtworks.go.plugin.access.notification.NotificationExtension.notify(NotificationExtension.java:82)
at com.thoughtworks.go.server.messaging.notifications.PluginNotificationMessageListener.onMessage(PluginNotificationMessageListener.java:44)
at com.thoughtworks.go.server.messaging.notifications.PluginNotificationMessageListener.onMessage(PluginNotificationMessageListener.java:29)
at com.thoughtworks.go.server.messaging.activemq.JMSMessageListenerAdapter.runImpl(JMSMessageListenerAdapter.java:83)
at com.thoughtworks.go.server.messaging.activemq.JMSMessageListenerAdapter.run(JMSMessageListenerAdapter.java:63)
at java.base/java.lang.Thread.run(Thread.java:833)
At startup the server logs an exception. Plugin seems to be not initialized because of that.