To find metrics for an EC2 instance and check if it's Unsupported or having None recommendations.

Compute Optimizer is indicating that the instances you queried are likely already well-provisioned and optimized for their current workloads.

If you're receiving empty recommendations for instance types like "c5a.xlarge," it could mean that Compute Optimizer did not find any performance improvement opportunities for these instances. In such cases, the tool does not suggest any specific changes because it determines that the instance is already well-provisioned.

It could also mean that it does not have enough metrics to come to a recommendation.

Amazon EC2 instances require at least 30 hours of metric data in the past 14 days. If you enabled the enhanced infrastructure metrics feature, EC2 instances require at least 30 hours of metric data over the past 93 days.

This is a snippet of the AWS documentation

If your resources don't have enough metric data, allow for more time before the recommendations start appearing in the Compute Optimizer console. For more information about the metrics that Compute Optimizer analyzes, see Metrics analyzed by AWS Compute Optimizer.

Suppose that your resources have enough metric data, but the recommendations aren't showing up. This probably means that Compute Optimizer is still analyzing your resources. It can take up to 24 hours to complete the analysis. After the analysis is complete, resource recommendations appear in the Compute Optimizer console.

Link for the document - https://docs.aws.amazon.com/compute-optimizer/latest/ug/requirements.html