After installing the Amazon SNS Notify plugin and providing a global configuration, jobs report the following errors in the Jenkins log when run.

RunListener failed
java.lang.NoClassDefFoundError: Could not initialize class com.amazonaws.ClientConfiguration
at com.amazonaws.services.sns.AmazonSNSClient.<init>(AmazonSNSClient.java:128)
at org.jenkinsci.plugins.snsnotify.AmazonSNSNotifier.send(AmazonSNSNotifier.java:144)
at org.jenkinsci.plugins.snsnotify.AmazonSNSNotifier.onCompleted(AmazonSNSNotifier.java:85)
at org.jenkinsci.plugins.snsnotify.BuildListener.onCompleted(BuildListener.java:30)
at org.jenkinsci.plugins.snsnotify.BuildListener.onCompleted(BuildListener.java:8)
at hudson.model.listeners.RunListener.fireCompleted(RunListener.java:201)
at hudson.model.Run.execute(Run.java:1786)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)