https://devzone.nordicsemi.com/f/nordic-q-a/23832/valid-dfu-zip-containing-a-new-bootloader-nrf52I am running SDK12.3 on an nRF52 and the bootloader on my boards has no problem replacing the application through the DFU process. Now I found a mistake in the bootloader itself so I need to replace it. My build script for the replacement bootloader packageen-USTelligent Community 13Thu, 27 Jul 2017 14:05:49 GMThttps://devzone.nordicsemi.com/thread/93763?ContentTypeID=1Thu, 27 Jul 2017 14:05:49 GMT137ad170-7792-4731-bb38-c0d22fbe4515:9e9f8de1-5c58-4e94-a2bb-ab88afcfacccbjorn-spockeli<p>Happy to help!</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/93762?ContentTypeID=1Thu, 27 Jul 2017 13:26:04 GMT137ad170-7792-4731-bb38-c0d22fbe4515:e11c2404-f101-4b24-816b-b0715296fdb1Dan Danknick<p>Bjørn, the existing bootloader on my device was also &quot;--bootloader-version 2&quot; so changing my script to &quot;--bootloader-version 3&quot; created a .zip that transferred perfectly. Thank you for your help!</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/93761?ContentTypeID=1Thu, 27 Jul 2017 11:14:36 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3176de8e-3d56-489c-ab71-72981417067dbjorn-spockeli<p>Hi Dan, which version of nrfutil and nRF Toolbox application are you using? Also have you verified that the new bootloader firmware version is greater than (&gt;) the existing version of the bootloader on the device?</p><div style="clear:both;"></div>