I'm having the same issue - in the windows app I can find and click on any note and the preview of the note shows up in the note list, but when I click on the note the contents won't appear (it's just a blank screen). Closing and reopening the app doesn't solve the issue; the only fix I've found is restarting my computer. My app is up to date, although I first noticed this issue when the new version of the app was released. I would guess it occurs every ~2-3 days. Any suggestions?