Failed challenge response check while registering subscriber for notifications on GCP preshipping

Hi,

I am trying to register subscriber for receiving notification but getting bad request error.Also it seems that register service is not sending any request to challenge endpoint https://dataalloys.com/aw/notification/consumer

Here is the response of request

    "code": 400,
    "reason": "Bad Request",
    "message": "Failed challenge response check to GET https://dataalloys.com/aw/notification/consumer"
}

Endpoint

https://preship.gcp.gnrg-osdu.projects.epam.com/api/register/v1/subscription

Payload

{
  	"name": "alloysubscription",
  	"description": "Alloy Subscription",
  	"topic": "records-changed",
  	"pushEndpoint": "https://dataalloys.com/aw/notification/consumer",
  	"secret": {
  		"secretType": "HMAC",
  		"value": "testsecret"
  	}
}

Please let me know if something is missing from our side.