Waihon Yew

I have encountered a similar issue.
I followed a suggestion in the video to print the content of auth to the log file using Rails.logger.info auth at the beginning of the twitter action of OmniauthCallbacksController class.
From the log, I noticed Twitter returned an error as follows:

{"errors"=>
      [{"message"=>
         "You currently have Essential access which includes access to Twitter API v2 endpoints only. If you need access to this endpoint, you’ll need to apply for Elevated access via the Developer Portal. You can learn more here: https://developer.twitter.com/en/docs/twitter-api/getting-started/about-twitter-api#v2-access-leve",
        "code"=>453}]}

You might want to apply for Elevated access as suggested in the above error message.