I can see invocation metrics for my Amazon SageMaker endpoint, but I can't see the instance metrics

This happens when the execution role for Amazon SageMaker doesn't have the PutMetricData permission for CloudWatch. To resolve the issue, add "cloudwatch:PutMetricData" to the AWS Identity and Access Management (IAM) policy that's attached to the execution role.

To send instance metrics to CloudWatch, instances must assume the execution role. That's why the PutMetricData permission is required for instance metrics.