Application Services 3 not working - getting 404

Hi experts,

I am playing with the API and I am using the Postman to send the very first declaration with the example file in this link

https://clouddocs.f5.com/products/extensions/f5-appsvcs-extension/latest/userguide/quick-start.html

BTW, what is this ID field for and can I omit it? Can it be automatically generated or has to be specified?

         "id": "urn:uuid:33045210-3ab8-4636-9b2a-c98d22ab915d",

However, I am getting this error... What is this referer?

{
    "code": 404,
    "message": "",
    "referer": "10.146.199.144",
    "errorStack": []
}

Here is curl code converted by postman for the request

curl --location --request POST 'https://1.2.3.4/mgmt/shared/appsvcs/declare' \
--header 'Authorization: Basic xxxxxxxxxxxxxx' \
--header 'Content-Type: application/json' \
--header 'Cookie: BIGIPAuthCookie=xxxxxxxxxxxxx; BIGIPAuthUsernameCookie=admin' \
--data-raw ' {
  <With the example code in the above link>
}

Any idea where I did wrong? This is an F5 LTM instance deployed in Azure. The appsvcs plugin version is 3.26.1. I am also testing the Cloud Failover Extension and it works fine so the mgmt IP, authentication, ...etc all should be ok

Thanks,

Difan