Next Button not appearing

Hi Hero's - hopefully someone can assist me. I seem to experiencing a bug on the functionality of a "Next" button state. The way I've set up my training is one Scene offers the learner to select a button based on their role in the company, this then takes them to a new slide the outlines the type of training. I've set the state of the "next" button to be hidden when the created two buttons to choose from the timeline starts, and to be normal when the learner has visited both buttons. Initially this works well, however if I click previous on the slide and view the previous scene and go back into the slide it will not show the "next" button and the course can not continue even though the two buttons are in a state of being visited. Does anyone know what I can do to correct this?