Yea Krypto is right,
What you did wrong is selecting the wrong option on the event sheet.
Don't select "Compare instance variable" because this only codes for a number or a string
You should select "Is boolean instance variable set" for this codes for a boolean only.
Here's a screenshot to show you which option you should select:
If you have further issues be sure to ask.
I'm always here to help at anytime :D
Regards,
Radkampfwagen