https://devzone.nordicsemi.com/f/nordic-q-a/71961/testing-nrf52840-following-getting-started-with-nrf-connect-sdk-nrf52-seriesI am a beginner who just received nRF52840 and working through Getting started with nRF Connect SDK (nRF52 Series). Everything worked fine until I got to chapter &quot;Testing with a mobile Device&quot;. I received this error message: Building ‘zephyr/zephyr_prebuilten-USTelligent Community 13Thu, 25 Feb 2021 20:04:20 GMThttps://devzone.nordicsemi.com/thread/296387?ContentTypeID=1Thu, 25 Feb 2021 20:04:20 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9a726465-7d5e-4a17-8a12-4ae1f75c8864LuRocm<p>Thank you. That was the case.&nbsp; I have two chooses and no kit there is no indication of which one to chose. The first one work until I got to test with a mobile device. Anyway, it is positive to experience that there is help when needed.&nbsp;</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/295959?ContentTypeID=1Wed, 24 Feb 2021 08:43:00 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3e7b2a30-4d81-48bc-80b7-eb40e42c0870Jared<p>I just tested this and can confirm that it works. A common culprit is choosing the wrong board file :)&nbsp;</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/295946?ContentTypeID=1Wed, 24 Feb 2021 07:40:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0b6f1642-2e89-4362-a954-8f568f9ac5c8LuRocm<p>Found the solution this morning. Sorry for the inquiring</p><div style="clear:both;"></div>