Log from the doc - at the end from the process its blinking white (no wifi on):
! This device is not claimed to your Particle account.
! Resetting keys for a device you do not own may permanently prevent it from connecting to the Particle cloud.
? Skip resetting keys? No
Put the device in DFU mode
Tap RESET/RST while holding MODE/SETUP until the device blinks yellow.
? Select Continue when ready Continue
!!! I was unable to detect any devices in DFU mode...
Your device will blink yellow when in DFU mode.
If your device is not blinking yellow, please:
1) Press and hold both the RESET/RST and MODE/SETUP buttons simultaneously.
2) Release only the RESET/RST button while continuing to hold the MODE/SETUP button.
3) Release the MODE/SETUP button once the device begins to blink yellow.
Make sure your device is in DFU mode (blinking yellow), and is connected to your computer
>> i bring it in DFU mode, but Doc can't reach this and ends without a second try.
Error - No DFU device found
The Doctor didn't complete sucesfully. undefined
After I do it manually in DFU mode:
particle flash --usb tinker (this is the moment cyan and red appears again (I thought WiFi-credentials were cleaned by the doctor)
particle serial wifi
? Should I scan for nearby Wi-Fi networks? No
Attempting to configure Wi-Fi on /dev/cu.usbmodem1421
! Something went wrong: Serial port closed early
Status: fast cyan blinking with one red spot after 5 sec.
I found this solved thread with the same topic (should I give a try?)