Cornerstone not working when I edit pages

I have created a new website and installed theme x. I have installed the Icon 10 demo. When I click on the pages and then click on Edit with cornerstone I am getting this error:

Server Error
404
Page Not Found
This page either doesn’t exist, or it moved somewhere else.

I can’t seem to edit the pages with Cornerstone.

my website is aston41.com. There is only one plugin on the site that is activated which is the Cornerstone plugin. What can I do to make Cornerstone work?

Hi There,

Thank you for writing in, please update your XTheme to latest version 5.1.1. Then navigate to Settings > Permalinks and re-save it. This should resolve your issue.

Remember to clear all caches after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.

Cheers!