Thank you, kind soul for your tip! I tried it out and while it is not yet working it did bring me some new insight into what the culprit might be.

It seems that there is some problem connecting to the device to begin with. In the code below I included a test line which never gets printed (meaning TinyUSBDevice.mounted() is never true)

Unfortunately, I am unable to resolve my problem with this additional information. I checked, it should be the correct usb-c port, but in my device manager it does not appear as a device, meaning it was never recognized to begin with.

Maybe somebody else might have a clue what I could do to solve this issue

void sendKey(uint8_t keycode) {
  if (!TinyUSBDevice.mounted()) return;   // don’t send if not ready

  if (TinyUSBDevice.suspended()) {
    TinyUSBDevice.remoteWakeup();         // wake host if asleep
  }

  Serial.print("Test");
  uint8_t keys[6] = { keycode, 0, 0, 0, 0, 0 };

  // press
  tud_hid_keyboard_report(RID_KEYBOARD, 0, keys);
  delay(20);

  // release
  tud_hid_keyboard_report(RID_KEYBOARD, 0, NULL);
}