Particle Accelerator stacking

visionknight

When toggle powers like Concentration stack, there is a change in the icon that shows the number of stacks. I was playing yesterday and clearly applied Plasma Burn to an enemy (could see the icon on the enemy), but I didn't see the PA icon number change. Am I missing something?

legendarylycan

probably hit the internal cooldown; all forms can only be stacked once every 4+ seconds​​