YouTubeサムネイルが適用されない(認証されていないチャンネル)

{
  "status": "success",
  "id": "<videoId>",
  "thumbnail": {
    "action": "post",
    "status": "error",
    "code": 307,
    "message": "Your YouTube channel must be verified to set a custom thumbnail. Verify your channel at https://www.youtube.com/verify (phone verification). If your channel is already verified, try unlinking and re-linking your YouTube account to restore permissions.",
    "details": "<upstream message>"
  },
  "warnings": [
    {
      "feature": "thumbnail",
      "code": 307,
      "message": "Your YouTube channel must be verified to set a custom thumbnail. Verify your channel at https://www.youtube.com/verify (phone verification). If your channel is already verified, try unlinking and re-linking your YouTube account to restore permissions.",
      "details": "<upstream message>"
    }
  ]
}