Megane anti theft alarm issue

Could be a few things. By 'not working,' do you mean it's giving false alarms, or it just doesn't activate at all? Does the immobilizer seem to be functioning correctly? Have you had any recent power failures or battery issues?

It doesn't activate at all; no false alarms. I don't think it's the immobilizer because the car starts fine. And yes, the car battery was replaced last week.

Okay. The new battery might be the key. It is likely your alarm system is coded to activate the optical locking (indicators). I'd suggest going to a workshop to get it checked out, they'll probably just need to reset something in the computer.

Thanks for the advice. I went to a workshop, and you were right. The alarm system was coded to activate the optical locking. They recoded it, and it works fine now. Repair cost was 45€ Appreciate the help!