colemurray I ran into the same. On mac, the process to resolve was a bit different. Here is the steps I used to resolve: Download 10.15.4 here https://www.nordicsemi.com/Products/Development-tools/nRF-Command-Line-Tools/Download?lang=en#infotabs cp /Applications/Nordic\ Semiconductor/lib/libnrfdfu.dylib <PATH TO YOUR PYTHON SITE-PACKAGES>/pynrfjprog/lib_x64/ Run update_modem.py