I am experiencing this issue on WIndows 10 (all latest updates installed) as well. Fixed it by uninstalling the Evernote app, redownload from the MS app Store and install, re-login and the GUI is working correctly. I have had to do this a few times since the latest SW update.
Hope your SW devs can fix this SW bug ASAP...a BLANK WYSIWYG is a FAIL!
v 10.4.4 build 55 public
Editor: v112.1.14477
Service: v1.23.6
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