After replacing NAT instance appliances with NAT gateways, EC2 instances in a private subnet cannot reach the internet. Which of the following could be reasons for this failure? (Choose two.)

The application using an unsupported network protocol is a valid reason because NAT gateways support TCP, UDP, and ICMP. If the application attempts to use a different protocol, traffic will fail. A NAT gateway not showing an "Available" state indicates it's not operational, preventing any traffic from flowing through it. Incorrect options: NAT gateways do not have security groups associated with them; security groups are applied to the EC2 instances. NAT gateways must be created in a specific Availability Zone, and they are designed to be highly available within that AZ. Creating it in an unsupported AZ is not a typical failure mode. Port forwarding rules are not relevant here, as NAT gateways primarily handle outbound internet access for instances in private subnets, not inbound access to internal services.