Hi Kimabaghdasaryan.
Thank you, I created the second calendar and tested it before creating any events and am experiencing the same issue.
I started going through some of the newer security plugins we have installed and found the culprit. The bad boy was called “Disable Admin-AJAX” by LittleBizzy. If you’re curious, this is their description of the app, “Completely disables frontend access to admin-ajax.php regardless of Heartbeat settings, to avoid unwanted AJAX calls and vastly improve performance.”
Thanks again for a great app.