Nissan Micra airbag warning light?

nissan micra (03) 1.0ltr................I removed the front seats to give the car a good clean and after refitting them the airbag warning light is flashing . The odd thing is the cable under the passenger seat is not connected to anything, as the there is no cable attached to the seat ! Can't understand it as Iv'e only disconnected one cable connection , then refitted it ...ie ..under the drivers seat . Can you help please ?............Bob