I have this problem too. Evernote runs on my iphone and iMac and web browser fine.
I got a new Macbook air laptop. On the laptop, the evernote app has synced notes up to two months ago, and no further notes or changes to notebooks.
On the laptop, if I empty trash, the notes vanish, and then come back again.
I have updated the laptop software to the latest bigsur 11.0.1. Deleted Evernote, deleted all the logs and back ups, emptied trash, restarted, re-downloaded and reinstalled the app about 3-4 times, but the same issue remains. 3 devices have my up to date notes, and the laptop app seems to be frozen on a version from 2 months ago.
If I add a new note on the laptop app it will sync to my other devices.