It's hard to troubleshoot without seeing the .story file, but I'll give it a shot.
Best guess: Your trigger to change the button runs when a variable changes, but the variable doesn't change on the slide where that trigger is. Which means the trigger will never run.
Or there's something else wrong with the "when" of the trigger that changes the Continue button to Normal.
FYI: What you're describing is, in essence, a custom menu slide. Here's a post about those that might help: https://community.articulate.com/discussions/articulate-storyline/create-a-custom-menu-slide
