Matching Drag & Drop, States and Conditional Triggers.

I've had a little look around the forum but can't find an answer to this anyway.

I've built a quiz and am attaching conditions to the NEXT button trigger to prevent learners moving on if the question is unanswered and to trigger a callout explaining this. I'm ok with the multiple choice/True & False questions but can't for the life of me figure out the states of the Matching objects in the conditional fields. I've tried different combinations of Correct and Incorrect and Normal. 

I can stop the Next button progressing by specifying the matching objects to be either Correct OR Incorrect, and this works. However, I can't find the right way to get the callout to change state from hidden to normal!

Anyone any ideas?

cheers