Here is a solution that worked for me:
Uninstall the Evernote Web Clipper in Safari by navigating to Safari > Preferences > Extensions > Evernote Web Clipper and choose Uninstall.
From the menubar, choose Safari > Clear History and choose All History then Clear History.
On your keyboard, press ⌘ command + ⌥ option + escsimultaneously, then select Safari and choose Force Quit.
Restart your Mac.
Open Safari and install the Evernote Web Clipper extension from https://safari-extensions.apple.com/