NRF9160 DK. "Failed to protect B0 flash, cancel startup" when building and running bootloader sample

NRF9160 DK. "Failed to protect B0 flash, cancel startup" when building and running bootloader samplehttps://devzone.nordicsemi.com/f/nordic-q-a/58798/nrf9160-dk-failed-to-protect-b0-flash-cancel-startup-when-building-and-running-bootloader-sampleI understand correctly that in order to use my private key for my applications, I must first sign an immutable bootloader with this key and upload it to the device? I used this tutorial. I opened the samples/bootloader/ project.I did not find Use Secureen-USTelligent Community 13Fri, 06 Mar 2020 14:31:46 GMTRE: NRF9160 DK. "Failed to protect B0 flash, cancel startup" when building and running bootloader samplehttps://devzone.nordicsemi.com/thread/238560?ContentTypeID=1Fri, 06 Mar 2020 14:31:46 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b3551edd-65cd-4df0-88b1-385b5465aef4Amanda Hsieh<p>Hi, </p> <p>Please see shibshab's suggestion in this <a href="https://devzone.nordicsemi.com/f/nordic-q-a/56178/immutable-bootloader-private-key-in-zephyr">post</a>. </p> <p>-Amanda H.</p><div style="clear:both;"></div>