Device Blinking Dark Blue

Marking setup done using the Particle CLI 

This is by far the easiest and fastest way to fix the issue, but it requires a hardwired connection (via USB).

If you haven't already, install the Particle CLI (link). Then connect your Argon or Boron via USB, open up your computer's Terminal, and run the command:

particle usb setup-done

You can optionally specify the name or Device ID of a Device if there is more than one connected by USB.

If this does now work, please take care to place your device in Safe Mode. In order to enter Safe Mode, press both RESET and MODE buttons and hold them down together. Release the RESET button, and wait until the Status LED Blinks Magenta. Then release the MODE button. The device should start Blinking Green (connecting to the Cloud) and then (provided connectivity) Breathing Magenta (connected to the Cloud - the same as Breathing Cyan, but in Safe Mode). Once your device is in Safe Mode, try again.

Marking setup done from code

If the Device is remote, and if there is a tech nearby who can get the Device back online by running your setup configuration again, you can set the flag from code by flashing this firmware to your Device:

#include "Particle.h"

#include "dct.h"

SYSTEM_MODE(SEMI_AUTOMATIC);

void setup() {
	// 0x01 = setup done
	// 0xff = setup not done (go into listening mode at boot)
	const uint8_t val = 0x01;
	dct_write_app_data(&val, DCT_SETUP_DONE_OFFSET, 1);

	// This is just so you know the operation is complete
	pinMode(D7, OUTPUT);
	digitalWrite(D7, HIGH);
}

void loop() {
}

You only need to do this once, as the setting is stored in configuration flash.

Note: the above sketch was designed to be flashed as separate, preparatory firmware prior to production firmware. One should avoid including the DCT write above within your production firmware, as it could in some circumstances lead to DCT corruption. 

Marking setup done from dfu-util

You can also set the setup done flag locally using dfu-util. Put the device in DFU mode (blinking yellow) by holding down MODE. Tap RESET and continue to hold down MODE. The status LED will blink magenta (red and blue at the same time), then yellow. Release when it is blinking yellow.

Argon:

echo -n -e \\x01 > dummy.bin
dfu-util -d 2b04:d00c -a 1 -s 8134:leave -D dummy.bin

Boron:

echo -n -e \\x01 > dummy.bin
dfu-util -d 2b04:d00d -a 1 -s 8134:leave -D dummy.bin

You only need to do this once, as the setting is stored in configuration flash, unless you clear credentials (fast blinking dark blue), then you need to do it again.