Cannot recover nRF52840 USB Dongle (PCA10059

[vectr]

Two of mine nRF52840 USB Dongle suddenly stop working. 
I am trying to flash it via nRF52840 DK (v 2.1.0), Starting with recover command:

vctr:~$ nrfjprog --version
nrfjprog version: 10.23.2 external
JLinkARM.dll version: 7.88j
vctr:~$ nrfjprog --recover -f NRF52 --log nrf52840_dongle.log
Recovering device. This operation might take 30s.
[error] [ Client] - Encountered error -21: Command recover executed for 1938 milliseconds with result -21
[error] [ Worker] - Encountered unexpected debug port ID 15, expected 2
ERROR: Recover failed. Please make sure that the correct device family is given
ERROR: and try again.

nrf52840_dongle.log

I tried flashing it using different DK, nrfconnect, on different PC - nothing worked for me.
On two different Dongles it works all right.

I've noticed that on working Dongles i have 3.3V on C20 (DECUSB output). Not working - 0V 

[Edvin]

Hello,

Yes, the nRF52840 dongles has a bootloader that sets the regout voltage correctly, according to it's pcb layout. Please see:

 nRF52840 Dongle Programming Tutorial 

The section "Using an external debugger" is particularly relevant.

So if the UICR is erased (either due to an erase or a recovery), then you either need a JLink Pro or you need to modify the hardware on the dongle (cutting solder bridges). 

Best regards,

Edvin