What should the solutions architect do to fix this?
Check to make sure that only IPv6 was used during the VPC creation.
Create a new IPv4 subnet with a larger range, and then launch the instance.
Create a new IPv6-only subnet with a large range, and then launch the instance.
Disable the IPv4 subnet and migrate all instances to IPv6 only. Once that is complete, launch the instance.
Explanations:
Checking to ensure that only IPv6 was used during VPC creation does not address the problem of insufficient IP address space. The error indicates a lack of available addresses in the subnet, likely due to the IPv4 allocation or insufficient IPv6 configurations, not simply the type of addressing used during VPC creation.
Creating a new IPv4 subnet with a larger range addresses the issue of insufficient IP address space. This allows for more IP addresses to be available for launching new instances, which is necessary if the existing subnet is exhausted in terms of available IPv4 addresses.
Creating a new IPv6-only subnet does not solve the immediate issue since the error is related to insufficient address space in the existing subnet, which might be an IPv4 subnet. Moreover, if the application requires IPv4, this option does not resolve the deployment needs.
Disabling the IPv4 subnet and migrating all instances to IPv6 only is not a practical solution and would likely result in service disruptions. It does not resolve the immediate need for more IP address space and assumes that all instances can be converted without issues, which may not be feasible.
I conclude that the answer is:
Create a new IPv4 subnet with a larger range, and then launch the instance.