Next Button Trigger

Without being able to see your story, I'm pretty much in the dark, but here are a couple of guesses. These are things that could cause what you are seeing, and might actually be causing it.

If you set the initial state of NextButton to Hidden, its timeline doesn't start until the click changes its state to Normal, at which time your trigger changes its state to Hidden. Best practice would be either to set its initial state to Hidden, or Change its state to Hidden when the timeline starts on This Slide. I know a trigger of that sort defaults to the timeline of the same object, but that is seldom the best option.

After that, your trigger to change it to Normal should work when Picture 3 is clicked.

The other one is easier. If NextButton1 is Disabled, or Hidden (either by a trigger, or because its time on the timeline hasn't come yet), you can't click on it. Write your triggers like this:

If those ideas don't work, attach your .story file here, so someone can take a look at why it isn't working.