Since we haven't heard back from your side concerning the Post, We shall mark the Post as Resolved with the Action Plan to review if Traffic from your Machine isn't allowed to or from the Security Group linked with the VPC wherein the CML Workspace instances are deployed. Check if the Kubernetes Pods associated with the CML Workspace Kubernetes Cluster are Up/Running. If Yes, Such Exception should be reviewed from a Network Standpoint only.
You may reach out to your Customer's AWS/Platform Team to review the Traffic between your Machine & the VPC within which the CML Workspace is deployed.
Assuming your team fixed the issue outside of any Customer's Network concerns, We would appreciate your feedback to ensure our fellow Community Users can benefit from your experience.