Hi,
Actually, the default skin is not compatible with page builders out-of-the-box.
Those restrictions are coming from the fact that WP Customer Area applies some CSS resets in the area, to prevent your theme affecting the private area.
Please, follow this guide to disable that feature and allow you to use WP Customer Area with custom plugins into it.
Don’t forget to check our code snippets documentation to know where you should place that.
Side note: you’ll also need to wait for our next incoming release, which will include a bug fix that prevents WPCA post types to be selected in Elementor settings pages. Or, if you don’t want to wait, you can also edit the plugins files like described in this commit.
Regards.