What you show is an install not a run. Did you close the other Duplicati and start the service?
Again, check your About → System info → UserName if unsure. Also look at your StartedBy.
Duplicati will by default be at the usual location at port 8200, and you can browse directly to it.
http://localhost:8200/
Because the settings and databases are per-user, your change of user will leave them behind.
Migrating from User to Service install on Windows are more complete directions for this move, however you still have not done any testing to prove a permission problem before you started.
Lots of other unanswered questions remain too.