Bricked Autonomo by trying to get DevEUI

I’ve got 5 Autonomos and I successfully bricked two of those :confused: I am trying to onboard them onto a LoRaWAN network and tried to get the hardware DevEUI using a code I found on github. The code is

static uint8_t loraHWEui[8];
digitalWrite(beePin, HIGH);
uint8_t len = LoRaBee.getHWEUI(loraHWEui, sizeof(loraHWEui));
digitalWrite(beePin, LOW);

The Autonomos have become unresponsive since then and I wonder what did I do wrong and how can I undo it. Any Help is appreciated, I can post the full source of my program if necessary.

I got the other three Autonomos working by following this thread: LoRaONE device EUI
But two still remain bricked

Try putting the board into bootloader mode. This can be done by grounding the reset pin twice in a row (about half a second between). Make sure not to reset it a third time as that will put it back into normal mode. After a few seconds, the board should show up on the alternative COM port. Once you upload a new sketch, or a blank one, the board will then return to normal mode and show up on the primary COM port.

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That did the trick. Thank you very much.
Just out of curiosity, what did I do wrong?

The USB connection on other boards, such as the AVR one, is handled through an external chip (e.g. an FTDI one).

On the SodaqONE and the other SAMD21 boards, it is handled by the native USB support on the main processor. If a bad sketch is loaded onto the board, or if anything else makes the main processor become unresponsive, the USB also becomes unresponsive.