Would you be able to elaborate on this property you're referencing? Is this a custom Deal Property or are we referring to the HubSpot Score associated to the Contact object?
If this is the latter, this is a system property that cannot be manually adjusted via the UI or via the API.
If this is a custom property, would you be able to confirm your Portal Id and the Request URL you're using to make this request to update the property?
{"validationResults":[{"isValid":false,"message":"Property \"score\" does not exist","error":"PROPERTY_DOESNT_EXIST","name":"score"}],"status":"error","message":"Property values were not valid","correlationId":"6be135aa-16fc-4e66-b3b0-9f315c4a6241","requestId":"466546a0-e62a-4100-9a7f-ce33b7eef074"
}