Here is the obd2tool.com engineer solution to Mb Star C3 V2018.9 up DAS Xentry multiplexer initialization failed problem.
Initialization of diagnosis multiplexer failed.
The link between the diagnosis multiplexer and the diagnostic socket is interrupted.
The link between the diagnostic multiplexer and the diagnostic unit is interrupted.
The voltage supply at the diagnostic socket (circuit 30 and (or) circuit 31) is faulty.
When using SDconnect,check the connection status using the Toolkit.
1. First check if you use the correct software for Star C3 not sd connect c4, you do not modify software by yourself and it passes self-test.
If all these are okay, replace the Config file in c:\program\mecredes-benz\config
2.If still not work, check device and vehicle communication
3. Otherwise send your MB Star C3 and software back to repair.