I am having the same issue, first started occurring the other day. I went through the post above (Encryption key fix (fast cyan blinks with occasional red)) and I got ‘permission denied’ at the last stage. PSB the full output.
dfu-util: Invalid DFU suffix signature
dfu-util: A valid DFU suffix will be required in a future dfu-util release!!!
Opening DFU capable USB device…
Run-time device DFU version 011a
Claiming USB DFU Interface…
Setting Alternate Setting #1 …
Determining device status: state = dfuIDLE, status = 0
DFU mode device DFU version 011a
Device returned transfer size 4096
DfuSe interface name: "DCT Flash "
Downloading to address = 0x00000022, size = 608
Download [=========================] 100% 608 bytes
File downloaded successfully
attempting to add a new public key for device 5**************3
Error sending public key to server: Permission Denied
Make sure your device is in DFU mode (blinking yellow), and that your computer is online.
Error - undefined
It then started blinking green, fast. I searched around as you do, and ended up running the following commands, which seemed to change the way it behaves (at least the LED blink sequence):
particle keys server cloud_public.der particle keys new photon particle keys load photon.der particle keys send photon.pub.pem
This seemed to (sort of) work, but upon reboot it now flashes cyan fast, then yellow slow 3 times, then repeats, occasionally blinking fast green between every few sequences. I have attempted to add my device via the normal method via the app but no joy, I get the following message:
Your device has been successfully claimed to your account, however it is offline. If the device was already claimed before this setup then the Wi-Fi connection may have failed, and you should try setup again. ’
This is the same message I have got since attempting to get this back online again.