The first step under “Testing for Conflicts Guide” instructed me to activate the Twenty Sixteen theme. This WordPress base theme had been deleted from my themes area about a year ago, and when I today downloaded and re-installed the 20/16 theme, the problem issues with the Event Calendar were instantly solved. My site is running a Genesis child theme, and I guess I was not aware that the old WordPress 20/16 theme needed to be permanently installed (though not activated) for my site to properly run.
Thank you for the quick response! I will definitely renew my Pro license this month!