Unless you have a Sunlight Chamber equipped to that specific spell/ability, it will only activate when the FOF circle is 'colored', which shows that the fonons are highly dense. Using a Sunlight Chamber allows use of FOF attacks, even IF the circle is only white.

If you're still having trouble, and the circle is colored, then you're just using the wrong ability, as each spell/ability will only have one FOF that will activate it. (i.e. Water won't activate Lightning Tiger Blade, and Wind won't activate Rending Quake, ect.)