Custom Dropdown field is not populated in ticket.

Hi I am using the following endpoint 

/api/v2/requests

to create zendesk tickets on our account. We have the tickets creating correctly and correctly populating a number of custom fields. But one of our fields does not seem to populate. The field in question is a drop down field with multiple possible values.

I am following the docs here around custom fields.

https://developer.zendesk.com/documentation/ticketing/managing-tickets/creating-and-updating-tickets/#setting-custom-field-values

and like I said other custom fields are working correctly. 

I have attached the below json of the custom field that we are sending. 

```

{

  "custom_fields": [

      {

          "id": 10767612515085, "value":"orders__live_recording_request__order_fulfillment_"

      }

]

}

```

I have redacted the other custom fields from that json that are working. But for some reason when the ticket is submitted the field is never populated in the side bar of the form. I have double checked the id field is correct. E.g the form field id. And the value is the tag of the selected value. So at a lose for what I am doing wrong :(