Google Api Blocking Permission

I have been trying for almost a day to get this plugin to work, I have added the correct API Key and Calendar ID, I have setup the API referrer http for websites with multiple variations of the site url but I still just get this error.

While trying to retrieve events, Google returned an error:{
  "error": {
    "code": 403,
    "message": "Requests from referer \u003cempty\u003e are blocked.",
    "errors": [
      {
        "message": "Requests from referer \u003cempty\u003e are blocked.",
        "domain": "global",
        "reason": "forbidden"
      }
    ],
    "status": "PERMISSION_DENIED",
    "details": [
      {
        "@type": "type.googleapis.com/google.rpc.ErrorInfo",
        "reason": "API_KEY_HTTP_REFERRER_BLOCKED",
        "domain": "googleapis.com",
        "metadata": {
          "service": "calendar-json.googleapis.com",
          "consumer": "projects/258349141063"
        }
      }
    ]
  }
}
Please ensure that both your Google Calendar ID and API Key are valid and that the Google Calendar you want to display is public.Only you can see this notice.

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