The in5 WP embed plugin is designed to work with WordPress's Block and Classic editors.

Elementor, Divi Builder and other 3rd-party editor plugins, interfere with the in5 embed plugin, so in5 is not likely to work directly when editing with those custom editors.

However, there is a way to insert in5 content into these editors...

You can 

1) Create a draft post or page using one of WordPress' default editors (I recommend doing this in a separate browser tab so that you can keep it open).

2) Insert in5 content using the in5 embed plugin.

3) Access the underlying code (via the Hamburger menu > Edit as HTML in the Block editor, or via the Text view in the Classic editor).

Edit as HTML option in the Block editor

4) Copy the <iframe> code.

code view inside block editor

5) Switch back to your 3rd-party editor.

6) Add an "HTML" block, e.g., Code in the Divi Builder (left below) and HTML </> in Elementor (right below), and paste in the code.

The Code in Divi BuilderThe HTML in Elementor

Elementor content rendered

You'll likely immediately see your content as soon as you've inserted the code (image above shows content inserted into Elementor).