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If needed, disable access protection on the nRF5340 network core:
Code Block nrfutil device recover --serial-number <serial number> --core Network
Program the release image to the nRF5340 network core:
Code Block nrfutil device program --serial-number <serial number> --core Network --firmware thingy9151lite_nrf5340_cpunet_app_on_nrf5340dk_***_release.hex
Alternatively, program the application image from the build tree:
Code Block nrfutil device program --serial-number <serial number> --core Network --firmware thingy9151lite_nrf5340_cpunet_app/build/zephyr/zephyr.hex
Reset the network core:
Code Block nrfutil device reset --serial-number <serial number> --core Network
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