I need to run a group analysis but I don't know how to do it, the error always appears (print below). There are 3 groups ( risk_group) that I would like to insert as a class (LR = level 1, HR = level 2 and MDD = level 3) and I would like to control for sex, age and total brain measure. Please, if anyone can help me understand what I'm doing wrong, I'd really appreciate it. 

The FSG file is attached
Thank you.