Hi,
Thanks for using the Events Calendar.
Here on the pre-sales 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 before going to the WordPress.org forum I would look into this two guides and see if that helps narrow down the issue:
Testing Conflicts With Themes and Other Plugins
Fixing HTTP 404 errors
Thanks again!