I followed these steps, and the Duplicati Server appears to be starting on bootup now. Thanks for that.
When I try to open the Restore function in the UI, it reports that the database is locked.
What do I have to do about that?
EDIT: I’m sorry, I just realized this is a How To thread. And I just admonished people for doing the very same thing over on Plex’s forums. I should have started a new thread in Support. Can you break this off into a new thread?
Heh - no problem, sometimes these things all run together. 
Is it possible there was a backup running when you tried to do the restore?
If not, I think I recall reading something about the database being locked after aborting a backup (apparently some thread doesn’t get shut down and holds the database open). Did you maybe cancel a backup just before trying the restore?
That must have been the problem. I was able to restore a file today.
Glad to hear it’s working!
I’ll flag that post as the solution but please let us know if it happens again.
FYI a related forum post is Restore fails with “Failed to connect: The database file is locked database is locked” and it links to GitHub issue #3445 where there’s some discussion on what might cause it, and the issue priority.