True/False variable or trigger not working

Hello,

I have created a true/false variable to 'disable' the next button until the timeline ends (changing the value to True). I set the variable as false and added a condition to the next trigger, but it only works on one slide.

Attached are screenshots of my triggers and variable for both screens (the first one only works when I preview my course). I have tested the variable by inserting a text box and reference, and the variable works on both screens, but the user can still click on next before the timeline ends.

Help would be appreciated as I am going crazy trying to figure out why it works on one slide and not the other! Thanks