Renault Central locking will not lock using remote or button inside car?

We have a year 2000 Renault Scenic and central locking has decided not to lock anymore. Remote unlocks car ok but will not lock car (signal getting through as red padlock lights up and locks rear glass door). Button inside car also will not lock car (unlocks ok). Have checked all solenoids in doors and rear hatch, all work ok (confirmed by swapping polarity of connectors and lock ok). Seems to be no voltage coming from switch when press lock. I do not know circuit diagram and where relay for locking is? Any ideas please? Thank you for your help.

Rob
January 2008