Working with Divi Theme

Cant appear to get the plugin to work using the Divi theme.

I’ve tried two seperate divi sites and both having the same issue.

I can set a page as draft ok. But when I come to publish we get the following message:

An error has occurred while saving your page. Various problems can cause a save to fail, such as a lack of server resources, firewall blockages, plugin conflicts or server misconfiguration. You can try saving again by clicking Try Again, or you can download a backup of your unsaved page by clicking Download Backup. Backups can be restored using the portability system while next editing your page.

Any ideas?

Thanks!