Pokémon Legends: Arceus has received a new patch, bumping the game up to Version 1.1.1. The main purpose of this patch is to fix a bug with the Shiny Charm. This bug would prevent some players from receiving the Shiny Charm in Laventon. Once updated, this issue should no longer happen.
Anyone who was impacted by this bug should update their game, and then Professor Laventon once again to receive the Shiny Charm.