You need a diagnostic check first, preferably with the LEXIA equipment. That will tell you which part of the airbag system is faulty.

The usual suspect are the wires under the seats, but no point spending time or money looking here if its something else, like the driver's airbag.

Google "Lexia diagnostic map" or "Peugeot diagnostic map" for details of fellow owners with the equipment, who won't charge an arm or leg.