Hello Meriem,
Can you please tell me about other Events for same BO. Is it activated. A green light shows that it is activated and red shows it's not active. And same is updated in the Event linkage table. So Just check with other whether for same event and BO any other approval level is active. Also would like to know about the expression you are trying to maintain as I am not sure what exactly you are trying to maintain here . Could you please explain on that part as well.
Thanks
Gaurav Gautam