Hey @Hubert_Zwiercan, thanks for replying.
So I’ve just flashed the CORE2 as well, the L1 LED does blink now.
I’ve redone the whole adding the device process to the cloud two times again, to no avail.
The model I’m using is the Raspberry Pi 3 Model B, the one you can order from your website. I’ve actually ordered two CORE2-ROS with the Raspberry, the other one is working but the other one has problems.