Create an overlay linked by a scoreboard

Hello,

I would like create an overlay linked by a scoreboard. I explain me :
I actually create an adventure map and, at one point, i would like flash a picture at the center of screen during a quest dialogue.
For this I created an overlay, being the support of the image, which is triggered when the Troll variable is true. To be able to change this variable to true, I created a procedure testing the value of a scoreboard (troll).

Therefore, I can make my image appear when my score is a 1 and make it disappear when it is a 0. At least that's what I'd like...
I join pictures.
Could someone help me find my mistake?https://we.tl/t-nIiSM89NDs