But was that the base version or an upgrade that it ran? Upgrades for non-service are said to go into an updates folder in the folder you show, but since they didn’t, try C:\ProgramData\Duplicati\updates
The repeated message about the update is normal (or at least not unusual), but if you said install and it
didn’t leave a 2.0.6.1 Duplicati somewhere, that’s odd. A later error on Activate is unfortunately possible. Solution for the web UI not being available at all is manual start. Have you tried stopping and restarting?
A tray icon right-click and Quit should clear all Duplicati processses out (typically just the usual pairing).
That’s the solution for a really old base version (e.g. 2.0.2.1). I’d still like to know if you have one that old.
Even if you don’t, it’d be nice to know what’s going on. If somehow the download just glitched and failed, About → General screen has a Check for updates now button that should let you try updating again…
Other suggestions are welcome.