Here comes the problem:
Initialization of the Multiplexer has failed
The firmware version of the Xentry Diagnosis VCI being used is too new.
Xentry VCI version is too new and is not compatible with 2021.06 xentry version.
Check your Xentry version (here is 06/2021)
Run Xentry VCI Recoverytool on the desktop
Select the corresponding VCI version and update