Hi @heplesser, welcome to the forum.
Can you post a screenshot of that?
What could be happening is that you are already running Duplicati somehow, and the TrayIcon is detecting this and trying to activate the other instance.
I have not heard this reported as an error before though.
This indicates that Duplicati is indeed running. Are you running Duplicati as a service? As a different user?
I think the first message is the launch problem, where one instance is already running as a different user than you try to start it with.
The second one is an attempt to log in without a valid password.
First, you need to figure out where Duplicati is running. I suggest stopping this, possibly using TaskMgr.exe if you cannot get a handle on the instance.
If you do not need to run as a Service, it should be a simple matter of starting Duplicati, and then it will show the start page where you can change the password. If not, right click the TrayIcon and choose “Open” and you can change the password in settings.
If you need to run as a service, let me know and I will try to guide there.