Do you get the warning missing post content module in Divi?
You get this message when you enable the Divi builder on a page, post, or product that is built with a template in the theme builder. If you go to Divi > Theme Builder then you have likely created some templates. In the example below I have created a template for all my Posts.
This means that all of my posts will have the same template. This will also mean that you cannot use the Divi Builder on the posts anymore because they are using this template and that is the reason you get the message Missing Post Content Module.
Missing Post Content Module Solutions
The solution is very simple, you cannot use the Divi Builder on pages that are using a template so you need to use WordPress standard editor for those pages. If you want to make changes to your template then you can go to Divi > Theme Builder and open the custom body of your template and edit the contents.
You can also remove the template from the Theme Builder and just use the Divi Builder on those posts. However, if you want to change the layout of your posts at some point then you need to change each post. If you have a template then only need to change that template and it will reflect on all your post.