Hi Lindsey!
Thanks for reaching out to us! Let me help you troubleshoot that issue.
First, could you please try flushing your permalinks by going to wp-admin > Settings > Permalinks and clicking “Save Changes”. Does it work after that?
If it doesn’t, please make sure you are using our permalinks best practices detailed in this guide > https://theeventscalendar.com/knowledgebase/permalinks-best-practices/
If you still experience the 404 pages, it could be related to a theme or plugin conflict, so to narrow the problem down please go through the steps provided in the testing for conflicts guide > https://theeventscalendar.com/knowledgebase/testing-for-conflicts/ and let us know what you find in the process.
We suggest you setup a dev/staging site so you can make all these tests without disrupting the live site. We also encourage to make a full backup of your site, both database and files so in case something goes wrong you can always restore your site.
Let me know how that goes.
Thanks,
Victor