I have this same problem. I right-click on a folder then click "Export Notebook" then click the "export" button, but for me nothing ever happens. I don't even see a "loading" indicator. It's as if the Export button just doesn't work or doesn't do anything.
I'm on Monterrey 12.6.1 on a Macbook Air. Using Evernote 10.70.2. I'm on the Free plan.