A few days ago I had an issue with a web site that required me to clear my history. As far as I can tell ever since then I have had an issue with the Evernote. When starting it up I get the top menu and NOTHING ELSE. I would try quitting and would observe the syncing notice. At some point I decided to try reloading a fresh version of the program from the app store. HOLY COW! That was an adventure. LOTS of errors and warnings! I eventually got the program to start, but got the same nonexistent screen.
By chance I learned that if I minimize the screen (that does not show!) I could then see it in the dock area. After selecting the docked program it would open up and allow data manipulation. If any other program would open over the top of Evernote or if the computer went to sleep I would need to minimize and reopen it to do any work.
I just remembered that I recently had my mac update the operating system that required a restart. I do not recall when this happened in the chain, but I do believe it was shortly before this started happening. Currently it shows 10.13.3 (17D47).