AWS: Target.FailedHealthChecks - Site always in "severe" state

Solution 1:

It seems the error was caused by a Heath Check for the Application Load Balancer, not the Elastic Beanstalk application. The ALB needs its target changing in a different place (see the documentation).

It was an easy fix once I knew that:

To modify the health check settings of a target group using the console

1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.
2. On the navigation pane, under LOAD BALANCING, choose Target Groups.
3. Select the target group.
4. On the Health checks tab, choose Edit.
5. On the Edit target group page, modify the settings as needed, and then choose Save.