If you can still unlock the vehicle using the keyless facility on the passenger side, this would suggest that the system is working correctly but that the sensor on the driver's side has failed. It may be a matter of resetting the system or replacing the sensor on the driver's side, but we would suggest either taking the car to your dealer or to an independent Toyota specialist who may be able to rectify the issue. You can find one near you using the Honest John Good Garage Guide here: good-garage-guide.honestjohn.co.uk/