I've noticed this when I was setting up my arcanist but I can't see any reason for it in the Arcanist class settings.

Any ideas please?

Interesting issue. I checked through the game system configuration - the cause here is that there are no 0-level spells per day entered for the class. This is not a data entry error as the source material also does not list these.

However, since the Arcanist does not track spells known in the way Sorcerers do, and we do not track spells prepared, the sheet finds no way for the Arcanist to cast 0-level spells and thus (incorrectly) presumes the class hasn't gained access to spells of that level yet. Just as there is no entry for level 9 spells for a level 4 character.

The solution here is to fill in 0-level spells per day according to the 0-level column in the Arcanist Spells Prepared table. I have done so for the campaign, and you should now be able to enter level 0 spells into your Arcanist spell book.

Thanks. I was wondering if it was something like that.