Hi,
Sorry for the issues you are having. We are unable to provide tech support on the pre sales forum.
For tech support issues on the Events Calendar please post in the Support Forum on WordPress.org:
The Events Calendar
The plugin should be working and you do not need Pro to create, update, or delete events.
If you are getting a 404 Error please look at your 404 Error Guide:
https://theeventscalendar.com/knowledgebase/fixing-http-404-errors/
And if that does not help please follow our testing for conflicts guide:
https://theeventscalendar.com/knowledgebase/testing-for-conflicts/
Thanks