Duplicati won't start: "This is likely caused by upgrading to a newer version and then downgrading"

In your solution, the step 1 of reinstall canary got Duplicati starting, so what problems remained?

With Canary I had the FTP problem mentioned before. Behavior was the same for first canary install and canary reinstall after attempted downgrade.

The error message should actually have given the numbers, which is another way to distinguish.

After downgrade, Duplicati crashed instantly without notification
These are the related Windows logs:

Application: Duplicati.GUI.TrayIcon.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.Exception
   at Duplicati.Server.Program.GetDatabaseConnection(System.Collections.Generic.Dictionary`2<System.String,System.String>)
   at Duplicati.Server.Program.RealMain(System.String[])

Exception Info: System.Exception
   at Duplicati.GUI.TrayIcon.HostedInstanceKeeper..ctor(System.String[])
   at Duplicati.GUI.TrayIcon.Program.RealMain(System.String[])
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at Duplicati.Library.AutoUpdater.UpdaterManager.RunMethod(System.Reflection.MethodInfo, System.String[])
   at Duplicati.Library.AutoUpdater.UpdaterManager+<>c__DisplayClass58_0.<RunFromMostRecentSpawn>b__0()
   at Duplicati.Library.AutoUpdater.UpdaterManager.WrapWithUpdater(Duplicati.Library.AutoUpdater.AutoUpdateStrategy, System.Action)
   at Duplicati.Library.AutoUpdater.UpdaterManager.RunFromMostRecentSpawn(System.Reflection.MethodInfo, System.String[], Duplicati.Library.AutoUpdater.AutoUpdateStrategy)
   at Duplicati.GUI.TrayIcon.Program.Main(System.String[])

Faulting application name: Duplicati.GUI.TrayIcon.exe, version: 2.0.8.1, time stamp: 0x663a135c
Faulting module name: KERNELBASE.dll, version: 10.0.26100.2161, time stamp: 0x31da495c
Exception code: 0xe0434352
Fault offset: 0x00000000000c831a
Faulting process id: 0x42EC
Faulting application start time: 0x1DB37728D8A103C
Faulting application path: C:\Program Files\Duplicati 2\Duplicati.GUI.TrayIcon.exe
Faulting module path: C:\WINDOWS\System32\KERNELBASE.dll
Report Id: 81ec4db2-5a3c-4d1d-8b4e-0ecf0e38da05
Faulting package full name: 
Faulting package-relative application ID: 

How do you start and run Duplicati?

Duplicati is automatically started after login to Win 11.

Trying to install releases without stopping old release can be more fragile. Is this how you install?

I wasn’t really paying attention to this but I would say the update procedure was:

  1. Duplicati showed a manual update in the UI, so I downloaded the MSI and started install.
  2. During installation the installer failed to automatically close the active duplicati instance.
  3. I think I then closed the active duplicati instance
  4. Clicked OK on the dialog window (restart may be required)
  5. Started Duplicati canary
  6. FTP not working, see other post
  7. There was a warning regarding deprecated FTP options, so I changed the configuration
  8. FTP still not working