Zoho CRM REST API - Download Attachments Returns Null

When attempting to download a file using the Zoho CRM REST API the json is returning NULL.

I first pull a list of attachement information using CURL:

curl_setopt_array($curl, array(

CURLOPT_URL =>"https://www.zohoapis.com/crm/v2/Potentials/################/Attachments",

CURLOPT_RETURNTRANSFER => true,

CURLOPT_ENCODING => "",

CURLOPT_MAXREDIRS => 10,

CURLOPT_TIMEOUT => 0,

CURLOPT_FOLLOWLOCATION => true,

CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,

CURLOPT_CUSTOMREQUEST => "GET",

CURLOPT_HTTPHEADER => array(

"Authorization: Zoho-oauthtoken $refresh_token",

"Content-Type: application/json"

));

This returns information as expected:

{
    "data": [
        {
            "Owner": {
                "name": "So Broken",
                "id": "###6044000036######",
                "email": "why@zoho.com"
            },
            "Modified_Time": "2021-03-30T17:43:41-07:00",
            "File_Name": "Broken.pdf",
            "Created_Time": "2021-03-30T17:43:41-07:00",
            "Size": "58949",
            "Parent_Id": {
                "name": "Me Broken",
                "id": "###6044000041######"
            },
            "$editable": true,
            "$file_id": "ays10bfd51###d1894c63a4d59db45#######",
            "$type": "Attachment",
            "$se_module": "Deals",
            "Modified_By": {
                "name": "Me Broken",
                "id": "###604400003######",
                "email": "why@zoho.com"
            },
            "$state": "save",
            "id": "###6044000040######",
            "Created_By": {
                "name": "Me Broken",
                "id": "###6044000036######",
                "email": "why@zoho.com"
            },
            "$link_url": null
        }
    ],
    "info": {
        "per_page": 200,
        "count": 1,
        "page": 1,
        "more_records": false
    }
}

I then grab the ID in yellow for use in the download: