2006 RX-8 central locking issue...Any ideas?

Hi all i have a 2006 rx8 and my central locking is not working so car wont lock with the transponder or key in the door. I have the red light on the dsh to say i have a door open i have replaced both door sensors,boot & bonnet mechanism but still nothing changed.

I replaced the battery in key but nothing if i disconnect the battery i can lock the car manually.

The red light with key symbol flashes away but car still starts fine.

Anyone got any ideas?