AWS Pinpoint REST "endpoint" api gives 403 error

Hey, I am trying to call the AWS Pinpoint REST API for endpoint, but I keep getting 403 Error.

{
    "message": "Unable to determine service/operation name to be authorized"
}

I've followed the tutorial to setup the postman collection via the Using Postman with Amazon Pinpoint developer guide, and all other APIs seem to be working fine. Only the endpoint APIs give the error.

I cross checked the permission of the postman user policy and it does have the endpoint permissions (e.g. getEndpoint)

I got the endpoint ID by exporting the segment (+vrkjeeo/***************)