It's possible that:
* They go by a different name professionally. Perhaps they use a stage name or have a different spelling of their name.
* They work behind the scenes. They might be a writer, producer, or director rather than an actor.
* They are newer to the industry. They may have only recently started their career in entertainment.
To get a more accurate answer, I recommend searching for Ari Welkom on IMDb (Internet Movie Database) or other movie and television databases. You can also try searching online news articles or social media to see if there's any information about their career.