CloudWatch metrics for Trusted Advisor

Hello.

To use Trusted Advisor, you must subscribe to Business support plan or above.
In other words, if you do not have an AWS support contract with Business support or higher, CloudWatch metrics will not be displayed.
https://docs.aws.amazon.com/awssupport/latest/user/aws-support-plans.html

If you have an AWS support contract, a Trusted Advisor namespace will be created in CloudWatch as shown in the image below.