Triggers, Javascript & Multiple Layers

Hi all,

I'm having an issue with a timed quiz. I have a Javascript counter (set to 40 seconds) on the base layer of the slide. Correct & incorrect answers trigger new layers & add or remove 5 seconds from the counter.

I'm trying to trigger another layer (quiz failed) when the counter hits zero.

I've tried a trigger on each layer that says show failed layer when the counter variable changes & = zero, but this does not work. I've tried setting the trigger to show failed layer if counter variable equals zero at start of timeline for each layer, also without joy.

I feel like I'm missing something really simple here- can anyone give some advice? I've attached the slide for reference in case the above info is confusing.

Will putting the counter reference on every slide do the trick? Or is there a simpler resolution?

Thanks!