@tfranssen
Hi and thanks for posting in the forum.
First up - the installation of the python dependencies is a function of the Duet Plugin Service. So the fact that it objected suggests there is some form of error and that could be related to permissions which in turn could account for the inability to resolve a file list (in general, often permission related).
Please include a logfile (DuetBackup) with -verbose set and, as well your overall environment (SBC OS and version, Duet versions etc).
If you stop the plugin, run this command in an OS console then attempt to restart the plugin, you will see progress / errors:
env SYSTEMD_LESS=RXMK /usr/bin/journalctl -f
