You need to progress other quests that raise nobility compliance. Complete other quests, and after you've done a few more nobility quests that are unlocked after other quests (you can see what quests unlock which other nobility quests in the progress tracker room.) you will be able to talk to Ayumi, and complete her favor.
A few other people have had this problem on Mac in the past. It's usually because their system denied permissions for the game to create new files within the save folder. Make sure that the needed folders have their permissions set to allow for files and/or folders to be created and edited. Though, after brief research, there seem to be some problems with the RPG Maker engine itself when it comes to how it works on Mac sometimes. If my solution doesn't work, there are a few existing threads with solutions on the rpg maker forums that work for most rpg maker games you can search for that might give you more information on what you need to do.