Google posted a notice that it will now show warnings in the Google Search Console rich results report for when your structured data does not define the location for an event. Google said it will "start enforcing location requirements for events."
Google wrote "for events marked as virtual only (eventAttendanceMode = OnlineEventAttendanceMode), providing any physical locations will trigger a warning." Google added that "for any event with a physical address, the address must be of type Place, not PostalAddress, or it will be an error."
This might lead to an increase in errors or warnings for those who use event schema on their pages, Google said "therefore you might see an increase in errors and warnings in Event items on your site."
During COVID, the event schema added virtual and postponed and cancelled and now with people going back to events, Google wants to start enforcing the location. The location can be virtual/online and if not, then a physical address.
Google started to show richer event results back in 2017. Google then added Search Console reports for event rich results in 2018.
Forum discussion at Twitter.