Getting access forbidden when calling a SendGrid API

Question

Trying to invoke https://api.sendgrid.com/v3/suppression/bounces (https://docs.sendgrid.com/api-reference/bounces-api/retrieve-all-bounces) and I get a message of "access forbidden".

I am passing in a valid API Key, which is from a free new account.

API: GET Headers: Authorization Bearer SG.xxxxxxxxxxxxxxxx Accept application/json

Response:

{
    "errors": [
        {
            "field": null,
            "message": "access forbidden"
        }
    ]
}