At level 23, Conjuration at level 31. Conjuring flame atronach doesn't always work even when majicka level is optimum. Is there some detail that I'm overlooking? When it works, it's great.
Is there any message in the top left corner? Is the targeting cross white? Are you targeting a valid location? (Free Space, flat ground)?
Also the conjuration spells have a maximum range.
Also the Atronach perk in the alteration tree, or the Atronach standing stone can cause that problem. The conjuration spell is cast upon oneself, so, you are absorbing a spell that is cast at you. Most people got caught out with this.
Unfortunately for Conjuration mages, the game treats summoning as a spell being cast on yourself, thus the 50% spell absorbtion chance kicks in making your summons 50% likely to not occur. PC Users can avoid this bug by installing the "All in 1 Spell Fixes Mod". Source
From the Conjuration UESP Wiki article: