Rebooting and reinstalling didn't work, so I contacted Support. It turns out that the Windows app has changed the way it is syncing in anticipation for a new sync routine that will be in the next release. Until then, the notes will only sync when it's time for the automatic sync or when the Sync button is clicked. Support told me that there will be more details when that version releases, so I'll wait and see - although instant sync is not indispensable for me, I found it really convenient, so now I'm curious about what they are going to change. Thanks for the help!