MOX - LED on module B

What exactly is functionality of LED on module B? The LED was on, but the module was not working.
I had here 2 different cases with 2 MOXes in netboot configuration A + B.

  1. lspci -vv was empty -> I needed to disconnect module B from A and connect them back to resolve this problem
  2. lspci -vv contain message about module cannot be found -> there is difference between mox filesystem and mox signed kernel.

In both cases MOX 5 GHz WIFI was not working.