How did you open the page you are developing? By going through the main page or just direct preview using Domino Designer?
Are there any error on the error pane in the designer? If there is, then you need to correct those.
Right-click your application in designer > Refresh > Build. Even if you set the Build automatically, sometimes it's best to "Clean" your application.
On your notes client workspace, before opening the app, press F9 to refresh the workspace. The try to open the app again.
These are just some of the things I tried if I faced the exact same problem as yours (even after restarting Notes). It might not work for your case.