For the lamp failure indicator check this.
On the 210 cars (new E class) the tailamps are bad about melting at the contacts for the bulb sockets.
Remove the pink sockets on both tailamps and see if the terminals on the tailight assy itself have melted into the plastic.
You have to look real close as it is'nt real obvious.
Maybe compare to the terminals for other sockets.
This is probably the problem.
Mercedes Benz Master Tech
ASE Master Technician
Owner of "Behind the Star Inc."