A company runs an application on EC2 instances behind a Network Load Balancer (NLB). A solutions architect added instances in a second Availability Zone and registered them with the NLB target group, but the operations team sees traffic only going to instances in the original Availability Zone. What is the most operationally efficient way to fix this?

The most operationally efficient way to fix this is to enable the new Availability Zone for the NLB. Network Load Balancers are zonal by default, meaning they only route traffic to targets in Availability Zones where they have an enabled subnet. If a new Availability Zone is added to the target group but not enabled on the NLB, traffic will not be routed to instances in that zone. Creating a separate NLB for the second Availability Zone would introduce unnecessary complexity and management overhead. Turning on proxy protocol is unrelated to traffic distribution across Availability Zones; it's used to preserve client IP information. Making a new target group is not necessary as the existing target group can accommodate instances from multiple Availability Zones once the NLB is configured correctly.