Hi,
Thanks for using the Events Calendar.
Here on the pre-sales & translation forum, I’m afraid we do not provide technical support. I would ask that you take any technical support questions across to our wordpress.org forum – our staff scan it periodically and other community members may also be able to help out.
The Events Calendar
Having said that:
Soft 404s are something we’ve gone back and forth with because of how tricky they are and how other users have told us how they prefer them to be handled:
https://theeventscalendar.com/knowledgebase/404_and_seo/
If you’re looking for a way to “fix” the 404s, then you can check out this post for more information on how to resolve returned 404s from the calendar. There is a snippet referenced in there that should help:
Fixing HTTP 404 errors
If you have more questions please post in WordPress.org.
Thanks again!