https://devzone.nordicsemi.com/f/nordic-q-a/76718/dfuHi, i am working on dfu with nrf52dk. i am facing a problem when genrating private key. in cmd i got error with following command &quot;C:\Users\admin\Desktop\a&gt; Traceback (most recent call last): File &quot;c:\users\admin\appdata\local\programs\python\python39en-USTelligent Community 13Thu, 24 Jun 2021 12:31:14 GMThttps://devzone.nordicsemi.com/thread/316988?ContentTypeID=1Thu, 24 Jun 2021 12:31:14 GMT137ad170-7792-4731-bb38-c0d22fbe4515:358c2042-059f-4d32-81b0-663d377bfa10Amanda Hsieh<p>Hi,&nbsp;</p> <p><span>That is</span><span>&nbsp;</span><a href="https://devzone.nordicsemi.com/f/nordic-q-a/65889/nrfutil-modulenotfounderror-no-module-named-constants/286320#286320">a known issue</a><span>&nbsp;with python 3.9.&nbsp;</span><span>Can you try</span><span>&nbsp;Python to 3.7?</span></p> [quote user=""]it replies &quot;mergehex command not found&quot;[/quote] <p>Please&nbsp;<a title="Installing the nRF Command Line Tools" href="https://infocenter.nordicsemi.com/topic/ug_nrf_cltools/UG/cltools/nrf_installation.html?cp=10_1_1">Install the nRF Command Line Tools</a>.&nbsp;</p> <p>Regards,&nbsp;</p> <p>Amanda H.&nbsp;</p><div style="clear:both;"></div>