2005 Renault Megane central locking

Electrical problem
2005 Renault Megane Manual 70000 miles

the dash lights show that the driver door is open all the time even when it's not. Because of this the central locking will not work.

do you know what is causing this to happen. If so is it expensive to fix.I want to avoid going to the renault dealers if possible. I've tried resetting the settings on the car and dis and re- connected the battery.