What should the solutions architect do to troubleshoot this issue?
Use a spread placement group. Set a minimum of eight instances for each Availability Zone.
Stop and start all the instances in the placement group. Try the launch again.
Create a new placement group. Merge the new placement group with the original placement group.
Launch the additional instances as Dedicated Hosts in the placement groups.
Explanations:
Spread placement groups distribute instances across hardware, limiting scalability within a single Availability Zone and failing to solve the insufficient capacity issue.
Stopping and starting instances in the placement group allows AWS to reallocate resources, potentially resolving capacity constraints and allowing new instances to be added.
Placement groups cannot be merged. Creating a new placement group would isolate instances, failing to fulfill the goal of adding to the existing group in a single AZ.
Dedicated Hosts provide dedicated hardware but do not address placement group capacity limitations, which are based on shared infrastructure constraints in the Availability Zone.
I design that the answer is:
Stop and start all the instances in the placement group. Try the launch again.