Can not delete transit gateway attachment - cli or console

Question

The TWG attachemnt is visible on the console, but canno delete it. 
aws ec2 describe-transit-gateway-attachments --region us-east-1 --transit-gateway-attachment-ids tgw-attach-0a50c5f5336a71c01 
{
    "TransitGatewayAttachments": [
        {
            "ResourceOwnerId": "23xxx", 
            "TransitGatewayAttachmentId": "tgw-attach-0a50c5f5336a71c01", 
            "ResourceType": "direct-connect-gateway", 
            "ResourceId": "8204dfd2-b0c7-4ae9-bce9-96998a191025", 
            "Tags": [], 
            "CreationTime": "2022-05-13T19:05:16.000Z", 
            "State": "available", 
            "TransitGatewayId": "tgw-0cbf474c3468f6204", 
            "TransitGatewayOwnerId": "231653829444"
        }
    ]
}

But if I try to delete - I get error
aws ec2 delete-transit-gateway-vpc-attachment     --transit-gateway-attachment-id tgw-attach-0a50c5f5336a71c01 --region us-east-1

An error occurred (InvalidTransitGatewayAttachmentID.NotFound) when calling the DeleteTransitGatewayVpcAttachment operation: Transit Gateway VPC Attachment tgw-attach-0a50c5f5336a71c01 was deleted or does not exist.

Anyone has any clue?

Accepted Answer

Thank you for the details.

As the attachment `tgw-attach-0a50c5f5336a71c01` seems to be a DXGW attachment, I'm wondering if TGW `tgw-0cbf474c3468f6204` has to be disassociated firstly from the Direct Connect console, following the steps listed [here](https://docs.aws.amazon.com/directconnect/latest/UserGuide/direct-connect-transit-gateways.html#associate-tgw-with-direct-connect-gateway).

Can not delete transit gateway attachment - cli or console

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