Place Bet error request

[Mikelevirgo]

Hi,
I'm trying to place an order through the Exchange APIs, this is my payload:

{
"marketId": "1.152870862",
"instructions": [
{
"selectionId": 48351,
"side": "BACK",
"orderType": "LIMIT",
"limitOrder": {
"size": 2,
"price": 1.11,
"persistenceType": "LAPSE"
}
}
]
}

I tried to place the order with the same values with the API-NG and it works fine, through postman I always have the same response:

{
"faultcode": "Client",
"faultstring": "DSC-0021",
"detail": {}
}

Could someone help me, please?