Goblin Bomb not working correctly?

[Tarpon]

Been enjoying the game, but maybe I'm just doing something wrong. I just got the goblin bomb, and it says to hold down R2 and push square to throw it. I'd say most of the time, I either just melee attack and then fire off the normal ranged attack. And if I keep it held down, the range attack will charge, and then again, pressing square will just melee.
I did get the bomb to randomly pop out like once or twice, but don't understand why. Any help appreciated.

[Lufia]

Did you perhaps have too little mana (the blue bar)?

[Tarpon]

Originally posted by Lufia:

Did you perhaps have too little mana (the blue bar)?

That was probably it. Didn't think to check.

[Ocumedes]

I had a similar issue but for me I hadn't realized I needed to hold R2 long enough for the ranged attack to charge up.