I have a 1997 C230 with 103 k miles on the clock, it has been serviced regularly by the Mercedes dealer since new, the car does not start anymore, it wasrunning well until both my remote keys stopped working, I manually opened the doors and tried to start the car but with no success, I called the Mercedes emergency service and they told me to point the remote key to the rear view mirror and activate the green light but this did not work as well.Please Help!

 

This is my know-how from owning different cars. I am new to Mercedes but hopefully this helps.

Does it try to crank? (Probably not)
-Check your fuses. Any fried or look banged up? Replace.
Try and determine if the key works due to the immobilizer (does it have a battery?)
Check your battery. On some cars, not sure with the Merc, but if it doesn't have a treshhold of voltage, it won't even let it crank.
-Do you have lights even?
Ignition Switch, check.
If you can, get an OBD2 reader and see if there are any codes, if the ECU turns on.

If not, or I suspect nonetheless, you have a sensor that is freaking out and telling your ECU not to start...Hopefully the OBD2 reader will say what it is.
Such as Fuel Relay or Main Relay

G-lcuk! Keep us posted.