Unable to retrieve OAuth access token

Twilio will start dropping webhooks until the authorization server provides a valid token.

• The authorization service is unavailable.
• The authorization service is unreachable.
• The client credentials you configured have been rotated or removed.
• The authorization server has started issuing a token which is not of type Bearer.

• Verify your authorization server is running and healthy.
• Verify your authorization server is not protected by a firewall which blocks the requests.
• Update the webhook settings with valid client credentials.
• Update the webhook settings to disable OAuth.
• Verify the authorization server issues tokens of type Bearer.