What should the Administrator do to resolve this issue?

Explanations:

Reviewing the application’s logs for requests from the VPC DNS address will not help identify the issue with the target group health check or the load balancer itself.

Reviewing load balancer access logs will help identify incoming traffic issues, but since the target group has no healthy instances, the problem likely lies with the health check configuration or the instances themselves.

The most likely cause of the issue is that the health check configuration is incorrect. If the health check fails, the instances will be marked as unhealthy, causing no healthy instances in the target group.

The listener configuration primarily handles routing of traffic based on the protocols and rules. If the target group is showing no healthy instances, the issue is more likely with the health check rather than the listener configuration.