Hi,
Sorry for the issues you are having.
There was a missing file that has sense been updated in 4.1.3 that caused this when using our older ticketing plugins.
Unfortunately, to regain access to the site you need to delete The Events Calendar in the plugin directory and then reinstall it from WordPress.org
To do that you need to use an ftp program, your hosts cPanel’s File Manager, or contacting your host to help.
The plugin is located here:
wp-content/plugins/the-events-calendar
And the latest version can be found here:
The Events Calendar
You can either search and add it back from the admin or follow these steps for manual updates:
Manual Updates
Sorry again for the issues.
Let us know how that works out.
Thanks