Serialport does not show up anymore - did I brick my GRAINS?

I think I made a horrible mistake - both of my GRAINS modules don't show up in the Port selection menu of the Arduino IDE anymore. The "Port" menu is disabled

I have tested different cables and I tried different USB ports. And I am still able to connect my other Arduino Nano development board.
So I think I broke both of my GRAINS modules


This is what I did: I wanted to see if the PINs can be used as output PINs and how much voltage I get from the outputs.
This is my sketch:
#define NUMBEROFPINS 8
int pins[NUMBEROFPINS] = {A0, A1, A2, A3, A4, 8, 9, 11};

void setup() {
 for (int i=0; i<NUMBEROFPINS; ++i) {
   pinMode(pins[i], OUTPUT);
 }
}

void loop() {
 for (int i=0; i<NUMBEROFPINS; ++i) {
   digitalWrite(pins[i], HIGH);
 }
 delay(3000);

 for (int i=0; i<NUMBEROFPINS; ++i) {
   digitalWrite(pins[i], LOW);
 }
 delay(3000);
}

I set all the PINs as "output" PINs in the setup()-routine and then alternate between setting them LOW and HIGH in the loop()-routine. After one of the GRAINS modules (serial port) stopped showing up in the Arduino IDE (and also in the Windows Device Manager) I wanted to double check what happened and uploaded the sketch to the other GRAINS module (which probably was a stupid idea).

Do you think it is possible that the code above disabled the serial communication?
Do you think there is a way to reset GRAINS? Or another way of connecting to GRAINS to reprogram it?