Sorry, I am not a computer expert, and I might not describe the problem properly. Please ask if there are further questions.
I downloaded Duplicati, defined a procedure, and started to save the data. After some seconds, I received the message “unknown error No transaction is active on this connection”.
On Source screen, where is the data coming from? Can a different small source selection do a backup?
On Destination screen, what is the Storage Type? Does the Test connection button report success?
If you changed the Options screen, please say how.
What’s in destination folder? I wouldn’t expect much after a few seconds. Can you confirm it’s empty?
Check the server log at About → Show log → Stored. Any reports there from about the time of failure?
After a failure, the Show log for the job’s backup usually finds no logs, but you can double-check that…
If problem is reproducible, you can watch About → Show log → Live → Verbose for some initial logging. Possibly Profiling level will be needed, but it’s very noisy, so I’m starting at a middle level that’s briefer…