Citroen Jumpy does not start

Hello, I have a Citroen Jumpy, I was driving quietly and standing in a semaphore suddenly and has not started again, take it to the official house and it has been there for a week and they tell me that they do not know what the failure is. I have knowledge and mechanics, but I don't know if someone can guide me what the problem may be. He has not presented any kind of symptoms, no noises, no strange fumes, nor Calenton. If someone could help me I would be very grateful, because I use it to work and I need it urgently ... Thank you very much