EDITED: THE ERROR STOPPED WHEN I CLOSED KM!
I happened to hit the keyboard combination (muscle memory, as it went to a previous macro) after I'd closed KM (left the engine running). The macro worked perfectly. I'm using Arc as my default browser.
Help! I've created this macro in KM, but when I run it, I get the following error message:
To confirm; the Action Failed alert only displays when KM editor is open AND KM engine is running, but don't get the alert when the editor is closed and only the engine is running? And the macro works in both situations?