To me, it looks like you're missing part of your variable syntax. You've referenced the variable name, but not the variable set. For example, if this variable was in a variable set named MyAwesomeVariables, the proper TOC syntax would be [%=MyAwesomeVariables.TITLE%]. Open the Variables folder in your Project Organizer, and see what variables file your TITLE variable is in. Then, add the name of that file to the variable declaration in your TOC entry.
Daniel Ferguson
Certified Flare Trainer & Consultant smartoutput.com