It is possible that:
* The name is spelled incorrectly: Perhaps there is a slight variation in the spelling. Try searching for variations of the name.
* The person is not a major celebrity: If Anselm van Melis is not a famous actor, it's unlikely they would have a readily available filmography online.
* The person may be involved in other industries: They may be an actor in theater, or work behind the scenes in film or television.
If you have any additional information about Anselm van Melis (e.g., their country of origin, a specific time period they may have worked in), it could help narrow down the search.