Hi,Unfortunately I cannot double-check with the mux because I'm travelling this week but I thought you cannot switch the mux off when it is connected to a car.
You did not provide any proof that your batteries are good. You may have new batteries but even new batteries may be bad. You should try to charge them fully and then load them properly to test how well they can supply current and how long. Try to use at least 0.5 A load for the test. Or try a new set of batteries.
It is a good idea not to connect your laptop to internet but for different reasons than your SW getting corrupt, if the SW has been properly configured. But you can use another hard drive to test the laptop just to test the WLAN interface.
Since you have inserted charged batteries to your mux, you've already done everything that can affect warranty, if removing the WLAN card from the mux would do that (when you remove batteries, the WLAN card is there and you can remove and reinstall it without any signs left that you did it).
The mux should work with a car with one cal.ini setting, both with the LAN and the WLAN connection (I've understood that exceptions exist) but now your setting is for WLAN.
Could you please help me. I have bought from china MB star C4 SDconnect and when I'm trying to connect on display show me "Device not in use". Is it broken MUX or not?