JLinkExe Cannot connect to J-Link via USB.

Hello,

I just got my nRF52832 DK and am following the Getting Started at the Infocenter to get familiar with it. Running Ubuntu 16.04 and all the latest Nordic tools (SDK 15 etc.). While the first steps where very easy - blinky precompiled - I'm stuck at the first step of "Compiling and running a first example" which is "Erasing the board" for multiple hours now. http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v15.0.0/getting_started_examples.html

At first, nrfjprog complained about a missing JLinkARM, but i was able to resolve it installing SEGGER IDE (if using command line tools that should not be necessary) and linking the contained library as described by the user gamnes in https://devzone.nordicsemi.com/f/nordic-q-a/9937/nrfjprog-wants-jlinkarm-dll-on-linux

Now nrfjprog does not complain anymore about the missing library, but if trying to erase the chip "JLinkARM DLL reported an error." is reported. See the log.log below.

I also found this topic https://devzone.nordicsemi.com/f/nordic-q-a/36374/cannot-connect-to-j-link-via-usb-on-ses-for-arm-3-40 and have installed the JLink tools seperately to connect to the device first, because the problem seems to be similar. But also JLinkExe complains:

JLinkExe -device nrf52832 -speed 1000 -if swd
SEGGER J-Link Commander V6.34a (Compiled Aug  8 2018 16:31:54)
DLL version V6.34a, compiled Aug  8 2018 16:31:24

Connecting to J-Link via USB...FAILED: Cannot connect to J-Link via USB.

Why is it so difficult to follow the first steps of the getting started guide? Do linux image files with a preinstalled nordic setup exist? I guess that would be the most easy way. Or does someone know another way to get around this?

log.log for nrfjprog:

--------------------------------------------------------------------------------
nrfjprog -f NRF52 -e --log
nrfjprog version 9.7.3
--------------------------------------------------------------------------------
nRF_open_dll
. nRF52_open_dll
. . nRF52_dll_version
nRF_enum_emu_snr
. nRF52_enum_emu_snr
. . nRF52_enum_emu_snr
nRF_enum_emu_snr
. nRF52_enum_emu_snr
. . nRF52_enum_emu_snr
nRF_connect_to_emu_with_snr
. nRF52_connect_to_emu_with_snr
. . nRF52_is_connected_to_emu
. . nRF52_enum_emu_snr
. . nRF52_connect_to_emu_with_snr
. . . nRF52_connect_to_emu_without_snr
. . . nRF52_connect_to_emu_without_snr:	JLink:	   ***** Error: 
. . . nRF52_connect_to_emu_without_snr:	JLink:	Cannot connect to J-Link via USB.
. . . nRF52_connect_to_emu_without_snr:	JLink:	  returns "Cannot connect to J-Link via USB."
. . . nRF52_connect_to_emu_without_snr:	JLink:	 (0011ms, 0284ms total)  
. . . nRF52_connect_to_emu_without_snr:	JLinkARM.dll OpenEx returned error 'Cannot connect to J-Link via USB.'.

nRF_close_dll
. nRF52_close_dll
. . nRF52_is_connected_to_emu
. . nRF52_is_connected_to_emu:	JLink:	T49482740 000:286 
. . nRF52_is_connected_to_emu:	JLink:	JLINK_IsOpen()
. . nRF52_is_connected_to_emu:	JLink:	  returns 0x00
. . nRF52_is_connected_to_emu:	JLink:	 (0000ms, 0284ms total)  
. nRF52_close_dll:	JLink:	T49482740 000:286 
. nRF52_close_dll:	JLink:	JLINK_Close()