I am using the example request of linkedIn

curl --location 'https://api.linkedin.com/rest/adPreviews?q=creative&creative=urn%3Ali%3AsponsoredCreative%3A123456789&account=urn%3Ali%3AsponsoredAccount%3A123456789' 
--header 'LinkedIn-Version: 202309' 
--header 'X-Restli-Protocol-Version: 2.0.0' 
--header 'Authorization: Bearer XXX' 

and I am getting:

{
    "errorDetailType": "com.linkedin.common.error.BadRequest",
    "message": "Invalid param. Please see errorDetails for more information.",
    "errorDetails": {
        "inputErrors": [
            {
                "input": {
                    "inputPath": {
                        "fieldPath": "account"
                    }
                },
                "code": "QUERY_PARAM_NOT_ALLOWED"
            }
        ]
    },
    "status": 400
}

I have also tried with valid creative and account Id. I know that the same support page mentions: Ad Preview is currently available to select Beta partners. Please request access to this API by reaching out to your partner technical support channel or https://developer.linkedin.com/support but I went through the loops and I got access 6 months ago.

What am I doing wrong?