I'm trying to add my domain to ZeptoMail but it's rejected

I checked the network tab and I'm getting

{
    "error": {
        "code": "TM_3601",
        "details": [
            {
                "code": "DE_150",
                "message": "Antispam validation failed for your domain in Accounts."
            }
        ],
        "message": "Request Denied"
    }
}

I've opened a case with number 159553519

Can you please check why It's rejected as I really need this service!