nrf52840dk not working, always Blinking LED5 and no appearance as JLINK on PC

[AndrewAWG]

LED5 is blinking very fast. no appearance on computer at all. nrfjprog --recover not reconvering, 
Tried another PC, another cable and no response at all. 

[Hung Bui]

Hi Andrew, 
Could you take a screenshot when you do nrfjprog --recover ? I want to see the error log. 
From what you described, it seems that the DK couldn't communicate with the PC.
Have you tried on another PC ? Did it work before ?
Please take a photo of the board.

[AndrewAWG]

Yes it was working perfectly. 
I tried different cables and PCs. Same behavior.