If you're getting a warning in your server's console that looks like Failed to load the "x" enchantment! Reason: specified group "y" does not exist!, it means the group assigned to the enchantment does not exist. This is most common when downloading pre-made enchantments from the marketplace. All you need to do is open the enchantments.yml, navigate to the enchantment in question, and change the group: string to a group that exists. All groups can be found in the groups.yml.