nRF52840 DK not visible to host computer in normal mode or bootloader mode.

[alexisa]

I have received a dev kit and am trying to connect with it over JLink. I have connected it to my computer via the J2 micro-USB port. SW6 is set to default and Power Source is set to VDD.

When powering the board on, LED5 is blinking rapidly and no other LEDs are lit. Also JLink cannot connect to the board via USB.

When holding RESET and powering the board on, LED5 is blinking slowly but there is no mass storage device named "JLINK" or "BOOTLOADER" detected.

I've tried with different computers (including Windows PC), different USB cables, restart but to no avail. It seems that no matter what I do, the host computer is not seeing the board. Is there possibly an issue with the board?

[alexisa]

Embarassingly, it was the cable. 3 of the cables I tried probably weren't carrying enough power to the device. With the 4th cable, LED5 is solid green instead of blinking rapidly and the computer can see the device.