Issue while posting the email attachments for GCC high

Hi,
I tried to post the attachments which are non drafts and has attachment of size more than 3mb. I have used following API to post the attachment : https://graph.microsoft.us/v1.0/users/{userId}/messages/{messageId}/attachments/createUploadSession

and got the below error. Whereas , when I used the similar API to post the emails after chnaging .us from .com, it was posted successfully. Can you help , how can I post these email attachments?

{
    "error": {
        "code": "ErrorInvalidRequest",
        "message": "The OData request is not supported."
    }
}