How did you change your app name?. Basically, what I am saying is that if you want to change your app name in the middle of project. What should be done to change it or have to start new project?
Whenever you make a change to your unoproj file do an uno clean right after that should work
You can set a Title in the .unoproj file to change the name of the app. See here for details.
(Renaming the .unoproj file is also an option, although a bit more brute force 