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

Thanks for helping. I’d like to poke at the problem of this topic, where original post was vague.

If you had a start problem as opposed to a problem with a specific backup, that might be from

as opposed to

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

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

Generally Duplicati should be good at new versions updating old databases. Reverse won’t work.

How do you start and run Duplicati? That may impact the different possible issues that may arise.

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