I had the same problem after upgrading to version 10 on Windows 10. I currently have 10.4.3. Immediately after updating, my notes were appearing fine. After a couple of days, when I started Evernote, all the notes were blank. I could create a new note, but not enter anything into the new note. When I tried to open the About Evernote window, that was also blank. Stopping and restarting Evernote did not help. Ending the task from Task Manager did not help. Finally, I restarted my computer. Now Evernote is working. We'll see how long that lasts.
- Eric S.