Xentry Ignition Enabler [upd] Now
This happens because authentic Mercedes diagnostic hardware reads a specific voltage fluctuation or encrypted CAN signal on pin 15 (Ignition) that clones cannot perfectly replicate. The sits between your multiplexer and the OBDII port (or between the multiplexer and the 14-pin round adapter for older trucks) to artificially generate this missing signal.
ECU flashing and software updates