Hello! It sounds like you might be having problems with the sync on the Windows app? If yes, try signing out and then signing back in again. Feel free to get in touch with us if you need help - https://simplenote.com/contact-us/.
I've been tried to find the app that is similar to IOS's 'Note', but so far no luck until I find this app !! What I like about this app is that you don't have to connect to Clouds. (1) You write notes with your Android (2) Simplenote automatically uploads that notes to their clouds when your Android's WiFi (and/or Data connection) is on. (3) That's It ! You can always check/edit your notes with your Android or PC, THAT SIMPLE! Thanx a bunch for this and keep up your good work, Simplenote guys ! Best,