It sounds like what you want is to use XMLNIL. This will export null object Properties as  xsi:nil="true". Then on import the default behavior is to set such a valued Property to be a new instance of that object with no Properties set. See Handling Empty Strings and Null Values | Projecting Objects to XML | InterSystems IRIS Data Platform 2024.3
for more information.

If this was tied to your Windows password and you recently changed it then you may need to change the credentials for the service.

Try searching for "Services" in the windows search box and open the app. Then find the service associated with this instance (I think it would be InterSystems IRIS Controller for LATEST) and open properties and go to log on tab. Change the credentials here to match your OS credentials and then try starting your instance. Hope that helps!