Peugeot 406 hdi ?

The power is not as good as it used to be in my car also the speedometer needle used to kick in and out now the clock has stopped completely. When I open the drivers door all lights come on in dashboard including radio. When passenger door opened no lights come on. Also my indicastor lights doesnt show on dashboard but lights still working outside. Mileage at 0000000 in car now.
Had the car to mechanic sent to Auto Electronic and Repairs centre. Connected car to 2 different computers told nothing wrong with car only car was not communicating with computer. He also changed the ECU and relay said mine was working.
Headed to another mechanic he was convinced it was ECU changed ECU relay key chip etc, still nothing.
Where do I go from here.