Error using Azure DevOps REST API and classificationnodes

I am getting an error message when using the Azure DevOps REST API (regardless of version).

Running POST https://dev.azure.com/{organisation}/{project}/_apis/wit/classificationnodes/Areas?api-version=7.1-preview.2

with a body payload

{ "name": "Very nice area" }

Does not execute and an error is returned.

"status": 415, "message": "TF400898: An Internal Error Occurred.....

From the MS article below I'd expect to have an Area created for the given Organisation and project in the URL. Note that I do not have an issue using other REST API calls to the same DevOps organisation.

https://learn.microsoft.com/en-us/rest/api/azure/devops/wit/classification-nodes/create-or-update?view=azure-devops-rest-7.2&tabs=HTTP

I've tried adding the path in the body and the URL and various versions of the API. I'm able to update work items in the same organisation. I also get the same error when trying Iterations as well as Area.

"status": 415, "message": "TF400898: An Internal Error Occurred.....

From the error message, the 415 status indicates Unsupported Media Type error. The issue could be related to the Post Headers.

We need to set the Content-Type to application/json.

You can refer to the following PowerShell script to run the Rest API:

$token = "PAT"



$url="https://dev.azure.com/OrganizationName/ProjectName/_apis/wit/classificationnodes/Areas?api-version=7.1-preview.2"

$token = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes(":$($token)"))

$JSON = @'
{
    "name": "Very nice area" 
}
'@

$response = Invoke-RestMethod -Uri $url -Headers @{Authorization = "Basic $token"} -Method Post -Body $JSON -ContentType application/json

If you are using Postman, you can refer to the following headers.