Getting error "Serverless Generic Compute Cluster Not Supported For External Creators."

[tonyd]

Getting the above mentioned error while creating serverless compute. 
this is the request 

curl --location 'https://adb.azuredatabricks.net/api/2.0/clusters/create' \

--header 'Content-Type: application/json' \

--header 'Authorization: ••••••' \

--data '{

"cluster_name":"server-less-cluster-postman",

"spark_version":"11.3.x-scala2.12",

"node_type_id":"i3.large",

"enable_serverless_compute":true,

"autoscale":{

"min_workers":0,

"max_workers":2

}

}'

Response - 

{

"error_code": "INVALID_PARAMETER_VALUE",

"message": "Serverless Generic Compute Cluster Not Supported For External Creators.",

"details": [

{

"@type": "type.googleapis.com/google.rpc.ErrorInfo",

"reason": "CM_API_ERROR_SOURCE_CALLER_ERROR",

"domain": ""

}

]

}