How to Require Users to Select Images in a Specific Order

Triggers are executed independently of each other, and in the order they are listed. What that means is that no matter what the states of the pictures, Sweep layer trigger is first, and it will always be shown. That will set its state, whether it should or not, whether the second trigger shows the Try Again layer or not.  You need to change the show Sweep layer trigger to  - Show sweep layer if state of  [other pictures] are all Completed,

Also, you may have trouble with this trigger:

The timeline only ends once, and if the learner hasn't clicked on all the pictures by the time it does, they will never move to the next slide. I would suggest putting the Jump to next slide trigger on the Sweep layer, so when they are through with it, they can click something and advance.