Assistance with disabling/enabling next button

Hi everybody,

I've been developing a training that has a main "hub" slide with 6 topics. Clicking on a particular picture selects that topic. Once that topic is complete, it returns you to the hub slide. I'm trying to resolve the following:

I need the next slide arrow to be hidden on the hub slide, and appear only when all topics have been selected. So far, my efforts have not worked. I have successfully hidden the next button (hide next button on timeline start), but after clicking on each picture it does not change the state of the the hidden next button to normal despite a trigger stating to do just that (change state of next button to normal when all of the pictures are visited).

Can anybody point me in the right direction, or tell me what I may be doing incorrectly? If anybody has created a similar training I'd be curious to see how you accomplished this. A couple more data points:

1. Each topic is a new scene

2. Clicking on the picture jumps to the start slide for that scene

Thanks everybody!