I followed this guide to integrate AWS CloudWatch with PagerDuty. I wanted to fire an alarm when Errors became greater than 0 for an AWS Lambda function, but when I triggered the alarm, CloudWatch successfully published a message to SNS, but an incident never reached PD. The same happened when I changed the CloudWatch alarm to monitor Invocations.
The problem is not the service or escalation policy, because if I attach an e-mail integration to the same service, a test e-mail will trigger a notification.
This old post suggests that CloudWatch alarms for Lambda metrics do not work, but alarms on metrics for CPU Utilization should work. However, when I tried the same alert for CPU Utilization > 0% on an EC2 instance, it also failed to fire.
Is the CloudWatch integration simply broken?