Are you an Italian national traveling from Italy to Brazil ? If yes, it can be your problem. Unfortunately, Italy prohibits travels to Brazil for its nationals if they don't have a compelling reason to travel. I have even heard from people unable to check-in on itineraries like MXP-CDG-GRU because of this.

Due to this regulation, it can be the reason why AF Italian agency does not want to issue your tickets automatically.

You can try contacting AF over the phone if you have a compelling reason to travel (work, medical, emergency, studies...). Or try to book an itinerary beginning in AMS or CDG for instance.