Within AWS Organizations, a SysOps admin is attempting to enable AWS Compute Optimizer and tag policies from the management account to apply across all member accounts, but activation of tag policies is unavailable. What is the most likely cause?

The most likely cause is that the organization has not been configured to enable all features. AWS Organizations supports two feature sets: Consolidated Billing and All features. To use advanced features like Tag Policies and AWS Compute Optimizer integration across member accounts, the organization must be configured with the "All features" option. Consolidated billing being turned on is a prerequisite for AWS Organizations but doesn't enable advanced features. Member accounts enabling tags for cost allocation is a best practice for cost management but doesn't impact the availability of tag policies at the organization level. Member accounts individually enabling trusted access for Compute Optimizer is not required when Compute Optimizer is enabled at the organization level from the management account.