Good evening Darnell and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the 404 error messages you are receiving.
I would love to help you with this topic.
Simply put, I believe the issue lies in the Permalinks setting in your wp-admin.
For things to runs smoothly (and for your SEO to be much nicer down the road), use of pretty permalinks is required: https://theeventscalendar.com/knowledgebase/permalinks-best-practices/
Let me know if that helps.
If not, would it be possible to get the URL to a sample event where I could run some tests ?
Have a great day!
Geoff B.