Your site looks great! I’m actually from the Atlanta area myself and think this could be a great resource!
Looking over the previous thread, can you verify that you’ve re-saved your permalinks on the the Settings > Permalinks tab? You don’t need to change any settings there, just re-saving what’s there will cause the rewrites to be flushed. This is typically the best solution for 404 issues on sites.
As a next step, would you mind re-downloading the plugin files from your account here, deleting the existing files on your server and uploading fresh versions of the plugin to your site?
If that doesn’t work, there are some additional steps (and possible snippet solutions) available within this Knowledgebase item https://theeventscalendar.com/knowledgebase/fixing-http-404-errors/ Let me know if any of this helps.