Configuration seems to have disappeared after reboot? has info and links relevant to Manjaro.
Duplicati team does not provide their package. If need be, you can contact packagers directly.
You might need to recall what workaround (if any) you did long ago to get their package going.
What user were you running Duplicati as before? Old backup files would show creating user.
Ideally you want to find a Duplicati-server.sqlite file somewhere on drive, dated at last backup.
~user/.config/Duplicati is the default Duplicati folder. The user might be you, root, or duplicati.
They might have used /var/lib/duplicati/.config. If you find the file, copy it to intended new spot.