Why is the Lambda function not being invoked?
A Lambda function cannot be registered as a target for an ALB.
A Lambda function can be registered with an ALB using AWS Management Console only.
The permissions to invoke the Lambda function are missing.
Cross-zone is not enabled on the ALB.
Explanations:
A Lambda functioncanbe registered as a target for an ALB. This is supported in AWS, so this option is not correct.
A Lambda function can be registered as an ALB target using either the AWS Management Console, CLI, or AWS SDKs, not just the Console.
For an ALB to invoke a Lambda function, the necessary permissions to invoke the Lambda must be in place. If these permissions are missing, the function will not be triggered.
Cross-zone load balancing on the ALB is not relevant to invoking a Lambda function. This setting applies to EC2 targets, not Lambda.
I design that the answer is:
The permissions to invoke the Lambda function are missing.