Just :
1. Right click on Windows task bar,and choose the "Task Manager"
2. Select ,"More details" and click on the Processes table option
3. Then look for Notezilla and click on "End Task" so that Notezilla closes.
4. Now try to run Notezilla again which will now appear in the taskbar in the tray area next to the clock.
NOTE: You can also try pressing the Ctrl+Shift+U and Ctrl+Shift+Q keys to check if you can create new notes, access your Notes Browser etc.