I want to share that I have this exact same experience and solution as well. We have been using the General Calendar layout for our achive shortcode for probably a year with no issues. Yesterday, I updated the plugin to the latest version and today the client reported the error message “there was an error while fetching events!” on their site. We looked at recent events added to see if there was something added that could’ve triggered an error, but did not find anything. We changed the shortcode layout to Full Calendar and it’s working and loading content fine. I tried a few other layouts, but none had issues fetching events, it appear to only be an issue with the General Calendar layout.
MEC 7.14.0
WordPress 6.6.1
PHP 8.1.29
Hope a future update resolves this issue as the client prefers the look of the general calendar.