Not sure if I was missing something but I kept getting destroyed before I was able to charge enough energy to fire my shot.
Viewing post in HOLD A TO CHARGE YOUR SHOT jam comments
You have to charge for about one minute.
I debated with myself a lot whether or not I should have something to let the player know how much longer they must charge. I ended up deciding not to to give it a more anxious feeling, not knowing how longer you have to resist. But people seem to be getting confused by it. It is what it is, lesson learnt!