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When you post a YouTube video with a custom thumbNail, the video may publish successfully while the thumbnail fails to apply. In this case the post’s top-level status stays "success" (the video is live), but the YouTube result carries a warnings array describing the thumbnail failure: 
{
  "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>"
    }
  ]
}

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Symptom

Your YouTube video appears on the channel, but the custom thumbnail you supplied is missing — YouTube uses an auto-generated frame instead. The API response returns status: "success" with a thumbnail warnings entry (feature: "thumbnail", code: 307).

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Most Common Cause: Unverified Channel

The dominant cause of a YouTube thumbnail 403 failure is an unverified YouTube channel. YouTube requires channel (phone) verification before it will accept a custom thumbnail upload.

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Fix: Verify Your Channel

  1. Go to https://www.youtube.com/verify and complete phone verification for the channel.
  2. Alternatively, in YouTube Studio go to Settings → Channel, select Feature Eligibility, and enable Features that require phone verification.
  3. YouTube may take up to 24 hours to enable custom thumbnails after verification. “Enabled” phone verification does not guarantee YouTube will allow thumbnail uploads — YouTube ultimately determines eligibility.
  4. Confirm you can manually upload a thumbnail in YouTube Studio. If you cannot do it manually, the API cannot either.

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Secondary Cause: OAuth Permissions

If your channel is already verified and thumbnails still fail with a 403, the linked YouTube account may be missing the required permissions. Try unlinking and re-linking your YouTube account in Social Accounts and grant all requested permissions during re-linking. For Brand / Content Owner accounts (often used for business or organization channels), make sure the linked account has the necessary permissions — we recommend “Owner” rights.

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Pre-Publish Thumbnail Requirements

Ayrshare validates the thumbNail before publishing where possible. To avoid a 307 thumbnail failure, ensure the thumbnail meets these requirements:
  • Format: PNG or JPG/JPEG. The file extension must end in png, jpg, or jpeg.
  • Size: 2MB or less.
  • Reachable URL: The thumbNail URL must be publicly reachable so Ayrshare can fetch it.
A thumbnail problem never fails the post. If a thumbnail is definitively invalid (wrong extension, confirmed over 2MB, or unreachable), Ayrshare skips it before the video is uploaded, still publishes the video, and reports the reason in warnings. If the failure can only be determined after the video is uploaded, the video stays live and the failure is surfaced via the same warnings array described above. Either way the video publishes and status stays "success".