My nRF5x DK kit has suddenly stopped working and I experience one or more of the following symptoms:
Please try/confirm the following:
If this doesn't help, please open a new case. In that case, refer to this one and once again confirm that you have gone through the ENTIRE list above.
If on step 4 the kit does not show up as "BOOTLOADER", try to download and install the mbed Windows serial port driver from here.