DEVIA Control Board TEST code – red LED and incomplete test

Hello,

I am fairly new to the Arduino world and my first project is the SPHERE-O-BOT (or EggBot, as named on Thingiverse).
I purchased the board and the steppers from the jjrobots page.
Devia Robotics Control board v1.0 .The enhanced Arduino Zero (jjrobots.com)
Stepper motor DRIVER (A4988) + heatsink > jjrobots (although mine are on red boards)

After I assembled everything and it didn`t work properly (servo doesn`t move correct, motors are buzzing),  I started to research and stumbled across the “Devia Control Board Test code”. I uploaded it and when I connect the board (power + USB), the blue LED next to the WiFi-module flashes one time and then the red LED flashed once, and after a two flashes of the red and green LED togehter, the red LED constantly stays on, green one is off. I tried it with and without the steppers on board (correct direction) – same results.
So I made my way the the serial monitor and I got this response:
TEST: Checking IMU…
WHO_AM_I : 11, error = 0
TEST: WIFI. Generating network JJROBOTS_TEST

Then it stops there and nothing else happens. Does anyone have some hints, what to do/try  next?

Some “additional” information (see also picture).
When I tested the EggBOT with Inkscape, I measured some voltages. Not much happened at the servo pins. GND and +5V were ok, but the 3rd pin for the signal only varied between 100 an 400mV when I changed the pen holder value in Inkscape (0-100%).
Another thing, which irritated me, was that the pins for the stepper motors have 12V on them. I thought that should be lower, as the operating voltage for the 17HS4401 stepper motors is ranged from 2.5 to 3V.

Thank you for any input!