Olá Vitor.
Eu fiz todas essas alterações e também adicionei esta configuração e deu certo, muito obrigado!
Step 1: Associate an IPv6 CIDR Block with Your VPC and Subnets
You can associate an IPv6 CIDR block with your VPC, and then associate a /64 CIDR block from that range with each subnet.
To associate an IPv6 CIDR block with a VPC
Open the Amazon VPC console at https://console.aws.amazon.com/vpc/.
In the navigation pane, choose Your VPCs.
Select your VPC, choose Actions, Edit CIDRs.
Choose Add IPv6 CIDR. After the IPv6 CIDR block has been added, choose Close.
To associate an IPv6 CIDR block with a subnet
Open the Amazon VPC console at https://console.aws.amazon.com/vpc/.
In the navigation pane, choose Subnets.
Select your subnet, choose Subnet Actions, Edit IPv6 CIDRs.
Choose Add IPv6 CIDR. Specify the hexadecimal pair for the subnet (for example, 00) and confirm the entry by choosing the tick icon.
Choose Close. Repeat the steps for the other subnets in your VPC.