According to the AWS Cloud Operations and Compute Optimizer documentation, Compute Optimizer provides right-sizing recommendations by analyzing Amazon CloudWatch metrics and instance configuration data. However, AWS explicitly notes that only supported instance types are included in Compute Optimizer analyses. If an EC2 instance type is newly released or not yet supported by Compute Optimizer, it will not appear in the Compute Optimizer dashboard until official support is added.

The documentation explains that “Compute Optimizer analyses only supported resource types and instance families. Instances using unsupported or newly launched instance types will not appear in the Compute Optimizer console.” This ensures the service provides accurate recommendations based on sufficient performance history and benchmark data.

While CloudWatch metrics are required for analysis, the complete absence of instances from the dashboard — rather than “insufficient metric data” notifications — indicates unsupported instance types. Compute Optimizer would normally still display those with limited metrics but would flag them as “insufficient data,” not remove them entirely.

Therefore, the most accurate cause of missing instances in this case is that Compute Optimizer does not support the newly released instance types, making option B correct.