This is happening for last few weeks- both Windows and MacOS clients.
Once i open existing Note - I get empty screen - for some reason Evernote is saving somethink. This can take around 10secons to recover and show content.
Still, why to do that in different way compared to Windows ? Right click to Notebook - Notebook settings - and modify name. In Apple OS this choice can not be selected for unknown reason (all Notebooks, none of them is shared)